So I can't say what your daughter is thinking, but I wonder if there's some negative experiences and associations here:
- Given that you've tried multiple delivery methods, some of them must have been unpleasant feeling for her.
- These medications also have unpleasant side effects in the past.
- Any time she does try to take it, she gets involved in a multihour fight with her parents.
- She probably doesn't feel any better with the medication beyond being told that she does.
Given all of that, taking the medication might be very stressful for her, even if she doesn't know why.
While I (autistic, but without pda as far as I know) haven't taken antidepressants, I have taken things like multivitamins. However, in my experience, actually taking pills is difficult. It's very unnatural to me to avoid chewing on "food" and swallow things whole. I have to do it quickly before my brain figures out what is going on, and I have to be in a good relaxed headspace. Out of interest, do other autistic people here feel the same?
I like to think of autism as being overwhelmed all the time. I can't say that that's how everyone feels, but that's how I model it internally. In another comment, you mentioned these issues starting when she changed schools. That's something that's overwhelming to any child regardless of their neurotype, even if the new one is better.
I wonder (and may be wrong) if the school change has made everything more difficult for her, which makes it more difficult for her to take medication (which was already difficult). So she gets stressed and physically feels unable to swallow the pills. And then she feels like you've made it a competition that she feels pressured to win (she has two options, "win" or take the meds, and she can't do the latter).
Anyway, I'm not a professional healthcare person, just a guy online, so don't take anything I say too seriously. Just airing out my read on the situation.