Birth grandparents' inappropriate comments

I take it these visits are unsupervised outings with the grandparents? It's a very difficult situation to be in. Perhaps having a conversation with them about how confusing that is, etc. In all liklihood, it won't make them suddenly have an epiphany that they have behaved wrongly...but it may give you an idea of where they are on the issue, so that you can decide which way to go from here.Is it possible, the next time they want to see her, to make it a large family function? That way you are there while they are & she sees everyone together. It may help her to see both of her families interacting together...but it will also allow you the chance to run interference a bit so that she can have the positive with them, without them interjecting the negative.