I concur with most of that, and I will emphasize even with a large well prebuffed strike force it would be incredibly risky.  Still, this might be a very rare opportunity to strike back at her.  Also, a clarification for Tanya, spells that create conventional illusions that appear externally, cause hallucinations, and interact with mindscapes are all usually classified as Illusions.  And it is a type of magic witches lack in, but spellcasters of Areelu’s caliber are known to sometimes incorporate entirely disparate forms of spellcasting and thus bypass such limits.

She said the date several times, ostensibly for notes she was dictating or memorizing. First one in 4715, last one I remember is 15th of Arodus 4718. I don't remember experiencing anywhere near that much time; I have many disconnected episodes, none longer than a few hours. I remember several different-appearing locations but none outdoors. There was one other visible person besides Areelu some of the time, she throws up an illusion of a dretch. I didn't have the tongues spell until later... 

Tanya doesn't quite understand the memory of Areelu saying 4715 AR, she didn't speak in tongues then but the meaning of those particular words comes through clearly. It seems to be an effect of the tongues spell she has now but she can't remember most of the rest of what Areelu said clearly enough to translate it, which is very suspicious!

I would really have expected to have grown enough to notice over three years. I remember her cutting my hair at the end to match the length it had when she abducted me, but I ought to be at least a couple of centimeters taller if I'm done growing.

The illusion could have been cast by someone else to frame her, or if she's working with someone, or - doesn't she have a whole organization behind her? Couldn't she find someone else to do illusions, even if this was her own project? 

Tanya would really hate to conclude that they learned absolutely nothing because the enemy could have fabricated any illusionary set of memories they wanted. Even if she shares the memory and they confirm it was an illusion, they won't know whether the illusion was cast by Areelu! On the other hand -

Why would someone have bothered showing me illusions - or suspected illusions - of which I could recall memories, unless they expected me to believe them? Illusions are a very obvious thing to suspect. Maybe the enemy is just toying with us. Is there a way for me to share the memories?

You can send more than just words over the telepathic bond, although it might take some practice if you’re trying to get an entire memory and not just images from it.  There are some more obscure and specialized spells that can transmit entire memories, but only a minute to ten minutes per spell depending on the exact spell.  So start with trying to use the telepathic bond and we can see if that will suffice?

The demon cultists don’t actually have that many high level spellcasters.  So getting someone that can create a greater mindscape or cast a permanent hallucination would be hard for Areelu, they are both 7th circle spells.  …well she could just cast from scrolls, but she would need to buy them and we’re unsure how much income she can earn acting anonymously.  If you were one of her main projects she could afford the expense even with our lower estimates on her purchasing power.

Also, lower circle illusion spells, such as audiovisual hallucination or major image might work, each casting can last as long as the caster can concentrate and Areelu should be able to get a caster that could help, but leaving absolutely no tells or flaws with them is actually a specialized skill.

As for you apparently not aging, there are standard known approaches for putting someone in stasis.  And Areelu likely has some nonstandard ones.

A point that might need clarification:  Outsiders like myself or like demons typically don’t have general spellcasting like mortals do, just a handful of innate spell-like abilities.  Whereas, to explain a few examples, wizards can cast any spell they can write in their spellbook and stably prepare, and witches can cast any spell they can teach their familiar and stably prepare, and clerics cast any spell their god can stably package and allow them to thus prepare (with some additional limitations from divine treaties on clerics’ list of available spells).  So even entire hordes of demons don’t have the range and versatility of spells available one high circle well-rounded witch or wizard might.

To put me in medical stasis she'd need a reason, Tanya thinks. A plan or contingency in which to use me, and either preparation or waiting for the right moment. So in addition to assuming she set me up, we should assume she chose the best time to act and wasn't constrained by having just met or captured me. Terendelev kept saying Areelu is known for complex long-term plans, and this fits. (Or someone else is framing Areelu; there's no monopoly on long-term planning.)

So the 'gods' are distributing magical technology unevenly between factions and classes, driving them to adopt different strategies and specializations. Tanya already knew they were fostering warfare and internecine competition; this makes it sound almost like they're simulating various equilibria... no, this is useless speculation at this point, for all she knows they just enjoy variety in their blood sports. 

I'll try telepathically broadcasting a memory, if it doesn't work I'll need instruction. Areelu standing over her, talking in a language Tanya didn't understand and now doesn't remember clearly enough to translate outside of a few words. Herself a prisoner in her own skull, tied down and not feeling or doing anything that feels important to the memory. Her native magic sense sensing many things that Tanya entirely fails to understand. A faint bitter scent.

(She has no idea how to send non-speech over telepathy but she has no real idea how to send speech either, it just works without Tanya being able to describe the experience in words, so she tries focusing on the memory while sort of - intending to share it.)

How much of that came through? Can you describe to me what you learned about the scene, what senses were included and what level of detail you got, or should I quiz you on details to make sure? ...maybe if you send me the same thing back I'll notice what's wrong or missing.

So we’re back to guessing at her long term plan, and if she really did wait that long she must have had one.  Could she have underestimated your abilities?  How thoroughly did she seem to study them?  Maybe she was figuring Deskari would kill me but you still save the city?  …And without my micromanagement your existence is well known and you become a publicly known hero?  I don’t see an endgame that benefits her out of all of that…  

The speech is coming through garbled, like you didn’t actually form a proper memory of it at the time.  Since dates came through… maybe you could try a memory with some numerical quantities, the wish wording I used supposedly actively divines that sort of information and restore the memory with it.  On my end I could obtain scrolls for divinations with retrocognitive aspects to see if any could recover the words from the garbled memories of them.  Maybe speechreader’s sight if you have a memory of her lips moving?

Individual elements of memory are all coming through clearly, just not all at once together.  Like I can get your magic sense or a bitter scent, but not all tied together.  Like here: [she sends back an exact reflection of what Tanya sent]

Speechreader’s sight needs the physical presence of the speaker.  But I think your general approach is along the right lines.  Your wish wording was obscure enough I don’t have an initial guess about spells to combine for enhancing the memories further, I will consider it…