I think its normal to have little crushes even while being in love with your partner but he is letting it effect everyone in the family and that can't be tolerated like others have said. Have you spoken to her about it? Yes your husband brought her into the house without you there but she obviously didn't say "i don't think its right to do this without your wife here". I think maybe she likes the extra attention so she isn't doing anything to stop it. I would talk to BOTH of them. Separately of course. But she obviously doesn't recognize the boundaries of marriage either. Or talk to the husband and have him talk to her. I don't think its only one party here. She has to know that he has this crush and apparently hasn't done anything to stop it.