MIL Advice

Alright so there is a chance that I am going to sound absolutely crazy, but if anyone has any advice I would greatly appreciate it. My husband is the oldest of three boys, the middle son has two daughters, we just had our daughter in November, and the youngest is now pregnant due in July. She has always treated us different and for the most part uses social media to do so. When we got married she put really nothing up but went through great lengths to brag about the other two. She is constantly sharing thing about the other grandchildren or the now pregnant future grandchild. It kills me. Well today while at BabiesRUs with them we were picking out things that over the past six weeks we needed. She goes and buys clothes for the unborn child after already purchasing things for the other two grandchildren. She has never once purchased anything for our child. When it was only me she was treating different it was fine but now that my child is involved I am getting upset. My husband and I are fighting more because he doesn't know how to confront the situation and honestly I don't either. If anyone has any advice I would greatly appreciate it.