Sarah, Just read this whole thread right now. I'm so sorry about what is happening. Trust me I went through the whole thing with Erik and his Mother and father....They were both a pain in the butt to the very end and now I don't talk to them much unless Erik is with me....lol.
I say you need to take the reins to this situation. Tell her that you both want the AHR and that they can help pay if they like but you will not have it at their house. You will be doing it somewhere else.
Erik and I in the very beginning were trying to accommodate everything for his parents but at the end I was crying just like you, Erik was arguing with his parents, it wasn't turning out great. So Erik and I both decided to f***K it and just have the wedding in Cabo, so we got up and planned our wedding in 2 months to have it in cabo. We also were going to have an AHR but since it was also getting complicated it never happened. Still bummed about that....
Anyways off the subject. You two are both adults, tell them that and you are putting your foot down.