Your second question is sort of complicated but it's definitely more like the second option than the first. What it means about susceptibility to one another's powers being governed by the narrative is...if your power says one thing should happen, and her power says a different, incompatible thing should happen, then which one actually happens comes own to which one would make a better story. 

A better story by whose standards?

That's sort of complicated! Yours and the other girl's, mostly, but not in a way where you can consistently affect the outcome by deliberately altering your narrative preferences.

...why is that an important warning to offer?

The last girl I worked with was a powergamer.

...the pen taps. She doesn't write anything more for a minute. Too busy thinking.

If I could rely on my narrative preferences absolutely, even in situations where they might change because of a developing understanding of how the world around me works and what sorts of things are possible in it, that would be a great comfort to me. If that is not so, then I am glad to know it, so as not to be falsely comforted.

If you take There's Another One, you can't rely on your narrative preferences absolutely in situations that relate to both you and the other girl, because they might conflict and yours wouldn't necessarily win. If your narrative preferences evolve naturally over time as a result of your growth as a person, then your new narrative preferences will be as reliable as your original ones were. The thing that doesn't work is brainhacking yourself to make your preferences more different from the other girl's in an attempt to pull the situation more into alignment with your original preferences. 

I understand. Thank you for explaining.

Are there any options for adjusting point total besides the listed Drawbacks? I am finding myself wanting more power than 70 points will give me.

It should be possible to create new Drawbacks, or nudge existing ones to give you more points. 

What do I need to know about trying that? Should I suggest drawbacks, or can you suggest them too? What factors govern the point reward of a drawback? What about mitigating an existing drawback so it rewards fewer points but is more comfortable?

In the realm of making existing drawbacks more lucrative, how might Decorative be augmented?

I can suggest drawbacks if you don't have any good ideas, but drawbacks you suggest are more likely to be useful! I'm not completely sure what you mean about factors, there isn't a specific mathematical formula that I'm applying to generate point values, I just sort of feel it, sort of like how humans are good at throwing things without learning about parabolas and vector mechanics. Mitigating an existing drawback might work. 

Augmenting Decorative...I don't have anything like that pre-loaded, I'll have to think about it. 

It's hard to know what to suggest when I don't know what makes something a drawback. But let's see...

Could Plain Jane be combined somehow with Style of Sisyphus, so that it's not that I will never be satisfied with my appearance but that I will continually be presented with inspiration to become restless about it while still appreciating what I have?

Could There's Another One be augmented if I have a specific narrative in mind that seems drawback-shaped? I don't want to say too much about it since I find this sort of thing works better if it isn't spelled out on the page ahead of time. So to speak.

Could Incomplete be mitigated so that it specifically does not apply to true loves? Likewise They'll Know?