I know exactly what you’re going through. Having a “God Warrior” of a mother in-law is horrible.
I have a question. Did you intend on mostly calling her by both names i.e. [name]Ava[/name]-[name]Marie[/name] when she’s born? If so, I think [name]Ava[/name] [name]Beth[/name] would be a good alternative, as it has the same feel and ring to it.
Alternatively, you could go with [name]Amorie[/name] or [name]Averie[/name]/[name]Avery[/name] as first names, and then pick a new middle name. (Note that the “A” in [name]Amorie[/name] is pronounced differently than the first “A” in [name]Ava[/name].)