Do you and your partner both live with her? If you do he’s probably seen something at some point. I think you do need to talk to him about it, especially if it’s affecting such important decisions for you as starting your own family.
When you say you can’t get away do you mean you won’t move out because of her problem? I think it would be a weight off your mind if you spoke to him.
I think it’s a conversation you should try to have before you get pregnant as it might involve some stressful decisions needing to be made.