Monster-in-law problems PLEASE HELP!!!!!!!?

I am going to give you a quiet run-down. I have been with my husband for over 9 years we had a son last year ( the first boy in there entire family for over 20 years) My mother-in-law and father-in-law NEVER make time to come see my son, we have asked them on many occations but they never come. They do though find time to visit there granddaughters oh everyday (no joke by the way) My husband tonight has asked if she could make time to take care of him so we can attend a wedding in 2 weeks and again this coming up weekend so we could go out biking. I said that I didn't want her to take him both weekends because I like spending the time with him, she then got on the phone and sorta bitched me out and also replied don't make this diffecult Samanatha and a bunch of other rude things !! I am just on the brink of never wanting to see her again, Iam I overreacting or what (this isn't the first time she has said something rude) Can any give advice on how to handle this PLEASE I BEG YOU!