M-i-l Won't Accept Daughter From Previous Relationship

I have been married 11 years and to this day I still have endless unresolved issues with my M-I-L. I'd like to first say that I have a daughter from a previous relationship and four children with my current husband. The four children are treated like treasures by my in-laws..they take them out, give gifts for Christmas and birthdays...but NOTHING for my daughter. Thanksgiving happened to be my daughter's bday. Yes we had pies for dessert but also got a bday cake for her as to celebrate her bday. During thanksgiving, my daughter and a couple other people overheard my MIL telling someone that she didn't know why we bothered getting my daughter a cake and we should have done this the next day..my husbands aunt offered to take my daughter shopping the next day and MIL said not to worry about it..when we sang happy bday MIL rushed the song and said hurry because we need to get this over with. My daughter revealed to me the next day that her feelings were hurt and after all these years of this treatment, she's tired. These treatment issues have come up in counseling we are receiving as I had filed for divorce a couple years ago due to my husbands constant attention to his parents..I felt neglected. It's almost as is we compete for his attention. I mentioned the Thanksgiving incident to my husband and he just blows it off..he says he'll mention it to her. I don't bother approaching her as in the past when I've talked to her, she has this mentality that she is never wrong. My husband has been in my daughters life since she was two, her own dad left. She considers my husband her dad as that is the relationship they have. This is just one of the many issues I have with her...but I'm really losing sleep over this one..enough is enough! Any advice?