"Come to think of it, science in general might be good for leveraging your miracle powers better."
Over the course of the next few days, Anaphiel acquires several textbooks containing salient information (not having experience with educating human children, she just picks ones that look relevant, not filtering for grade level), assures Mehitabel that if she's having trouble with something she can let her know and she'll explain or acquire lower-level background material, whichever's necessary, and finally determines that of her fellow angels on Earth only Haziel knows battery math, and begins tracking them down.
Mehitabel needs explanations and background for some of the more esoteric stuff, and she runs to the dictionary frequently too, but makes dogged progress, hopping every day between magic and science and history and Hebrew and reviewing her notes on her universe's metaphysics until she is reading by the light of her triple light spell.
Anaphiel finds Haziel and convinces (currently him) to tutor the Christ child in the mathematics of divine energy use, explains science, and reminds Mehitabel about recommended average number-of-hours-of-sleep per night for optimal brain development but otherwise does not attempt to interfere when she stays up late studying.
Can she see Haziel's wings too?
Haziel's wings are black speckled with white where Anaphiel's are red and a dusky purple where Anaphiel's are gold, with similar fading in between them. He's not as good at pretending to be human as Anaphiel is--his face is often expressionless and his voice is often toneless (his human voice, anyway; when he speaks Angelic he sounds as lively as anyone) and his body language is stiff, but he complies when reasonable requests are posed and he really does know his math.
Mehitabel does not require warmth from Haziel. She just needs to know how much divine energy she should expect various tasks to take under what conditions and what her recharge rate will be given various assumptions, and similar things about God and angels and anything else running on comparable battery systems.
Relevantly: Learning science will help a lot. The more she knows about how any given task works, the more of her own detail work she can do and the less energy it takes.
Interestingly, demons don't work the same way as Mehitabel and God and angels, but they work similarly in some ways. He will enumerate the technical details of the similarities and differences and why the similarities are important if she likes. One difference is how they recharge. The kinds of demons that do torture recharge from pain, succubi and incubi recharge from sex, wrath demons recharge from anger, etcetera.
Oh, dear. That makes it less likely that she will be able to reform the demons, doesn't it. At least the ones whose recharge mechanisms are particularly reform-incompatible.
If she is particularly determined, the source of the pain is immaterial. And masochists do exist.
If she is intending to do significant work with demons-in-general he recommends finding an adviser who is one of the not-actively-terrible kinds of demon.
"I'll find you one. It'll take longer than finding a magic instructor, but I can do it," she assures.
Now that Haziel knows that demons are an area of interest, he has some more technical detail on those, too.
How fascinating! (Demons are very interesting because if Mehitabel turns out not to be able to solve the technical problem of awful people going to Hell she may still be able to solve the social problem of Hell being full of demons making it particularly unpleasant. There aren't even that many demons.)
That is mostly not an option that has been considered before, largely because of the risks inherent in the prospect of getting the really nasty kinds of demons out of Hell to talk to.
Probably she wants to get large numbers of non-terrible demons on her side before she goes after the really nasty ones, though, since those are much more powerful.