Actually, for the time being, you aren't doing so badly. I don't like that you enter her stall and she puts her rump to you, but your using the passive ignoring technique was interesting. I don't think you would do this forever, but as you get to know each other, it doesn't hurt to experiment. And you work in the round pen is good.
The thing is, I do NOT beleive horses hold a grudge for you not being around, or you keeping her at your parents' house. That is just not true, to put if bluntly. But it may be true that you don't yet know each other, so a little experiementation will not be a waste of time. YOU, however, need to silence the guilt voices in your head. Otherwise, there will be too much noise going on in there for you to observe and hear what's goind on NOW in your mare's mind.
If the wait and ignore reverse psych thingy makes no change, then I would mix it up a bit. It's not that she is actually being aggressive, it's just that she doesn't see your being there as important enough to give it her full attention.
So, next time you are standing by the stall door and she won't even look at you or is hanging at the far side, make a little noise, like scuffling your shoe or tapping the door. When she looks at you, stop. when she loses that thought and goes away mentally, make a noise again. when she is ON you, you do nothing. when she puts her attention elsewhere, you interupt it. Do as little as possible to interupt. Just haveing her flick her ear at you, you stop. when she goes "away", and you start making a tiny interuption, give her a chance to come to you before you make the interuption bigger.
If you feel safe, do this inside her stall, but I might very discreetly have a whip by my leg, if I had the slightest feeling that she might charge. If she turns toward you and comes to you, pet her once or twice, (no big cuddling as it seems she is not a cuddler) and leave her alone, leave the stall .