D.B.
So sorry. Always a difficult situation. It's hard to know much for sure without knowing the math. How long have you 2 been together? How long have you been married? Do you have any children together? How long was he with her? How much time in between the 2 relationships? I can see how this info may not seem important but it is. These answers effect the actions to be taken and when. If your relationship is not as long as theirs was then you will need to be together for 4 or more years and have at least one child together before certain resistant personalities begin to give you legitamacy. If you have been together longer than them then you still need a child together to so called 'trump' her. I know this sounds rediculous but some people truly think this way. Whatever you do don't act like a wall flower when at gatherings. If they want to act weird then thats on them. You need to stand strong and appear comfident and secure. You only need to wait for their approval as long as enough to be polite about their position and standing. Other than that you don't need their approval. You should be able to share your feelings with your husband. Tread carefully if he doesn't see the problem at first. Don't make him defensive of his mom. It is his support and team work that you need. He can fix this where you may not be able to. It may take a while but once he expresses to you that he truly sees and understands the situation then wait a little bit and let him get sick of it. You be nice and be on his team. He has to be on your team or you lose. After a little bit longer you should be able to expect that he will defend you to his family and lay down the law. You are his wife and that other woman is not. You are in the family and that other woman is not. You are the one that makes him happy and if that other woman made him happy she wouldn't be his ex. On the other hand if she dumped your husband then why does his mother even like her at all. Your husband should have issue with this relationship between his mother and her either way. They are not allowed to be nasty or snide or anything less than wonderful to you or they simply won't receive visits from any of you. This needs to eventually be his stance to defend his family unit(him, you, and the kids). If the two of you do not a child together and will not be having one then the problem is a generation gap ideology issue and will be difficult to change because mom will not be changing her opinion that her son should be with his child's mother. But she should still be treating you well and he should insist upon it.
My husband dated the same girl from high school for 6 years. They had a child. My presence simply wasn't acceptable. Those 2 spoke all the time. He and I talked about it and his initial responses were understanding of his mom's behavior because they had known each other for so long and were close then. His mom had a big picture of my husband and his ex in her den. My husband honestly didn't think about it because it had been there for years. I never said anything about the picture. We had pictures made at about 1 year of marriage. We were listing how many we needed to give out and when he mentioned his mother I said I did not want my picture hanging in her house with his ex's. If he wanted to give her a picture of just him then that was his business. He just sort of sat there blank. He said he hadn't thought about it and agreed with me. We were having dinner with her at her house and he brought the pictures. She was all smiley and was claiming one of us together for her to keep. He told her that she could not have one until she threw away that peice of trash that is hanging in the den. She tried to defend her stance at first saying how that was such a good picture of the 2 of them (and it was), and how it reminded her of when he was younger. Basically, he made it clear that yes he was younger and obviously stupid or he wouldn't have been with her. Anyway the condition still stood that if she wanted a picture of us she had to throw the other one away. She did throw it away and now our picture is there on the wall.
Anyway, be patient, love you husband and be a team. Men don't see these women relationship things because men don't interact that way.
God Bless