Amber - I was in the same situation as you....my Dad passed away 3 years ago (Mum had died 9 years ealrlier), my sis (who lives in Palmy) and I had to clear out and sell their house - and my Dad was a hoarder with 30+ years worth of stuff in the house! Anyway, I digress....
It's been one of the most emotionally-charged, difficult things I've had to do - at times more upsetting than actually losing our parents

I think the problem is that all your childhood gripes and fights come back, and now it's like you're fighting for who loved your parents the most
We had to sell the house at well under what we had hoped, but there was almost no interest in it, the house needed much work, and the market was crashing (this was early last year). My sister didn't really seem to understand that just because we *felt* the house was worth more, that didn't mean we were going to be able to sell it for that. Fortunately once she was up here and able to see the house, she realised we just had to do it.
I think it's totally reasonable to want to sell the house - it would be far too upsetting to have it still in the family IMO; even if your sister does look after it.
I have found that (for us) actually being in the same room and talking about things helps alot. Because most of our communication is via email/text etc, it's very easy to misconstrue what it really being said. My sis and I are really not that close, we're just very different people, and we see things quite differently. It is such a hard situation to be in, when everything is so emotive. Can you get another family member (someone you both respect) to help discuss all the issues? Sometimes if everything is out in the open, and someone else is there to calm things down, you both might feel better?
Your sister is probably feeling guilty about the relationship she had with your mother, and is trying to make up for it, but no doubt it's coming out as something more hostile and passive aggressive!
Sorry for the novel, I just know exactly how you feel! I do know that now that the house is sold, and almost all of the crap in the house has been divided and sorted, we are getting along much better.