Really? Are you sure that's what she wants, some random hearing person to jump in and defend her? Is that what she needs? Do you know for a fact that even talking to the AP in private won't have some kind of negative repercussion for the teacher?
If you absolutely can't stand not to get involved, I think the first and possibly only person to talk to is the ASL teacher. But honestly, as long as the teacher was aware of what was said (i.e. it wasn't being said behind her back), I don't think it's anyone's business but hers whether she wants to correct the AP or let it go.
(This is all hypothetical of course; I realize Southern was not the OP.) 
