I would be FURIOUS and would definitely throw the food out, I wouldn't trust her for a second. What she has done is a total breach of trust. How dare she. I have a DD with allergies and NO ONE and I mean no one, should play about with allergies. What if she reacted badly to something she's feeding her, would she know what to do?
Good luck, I feel for you, it's a hard thing to bring up , hope it all works out for you xoxo