question about soon to be MIL

so I've been with my significant other for 16 years and always have had a good relationship with his mother, however since he proposed to me she has been distant and seems very disinterested in the wedding. Now I'm pregnant and she never asks about the baby. Our wedding is in a week and tonight she asked to have a family dinner with just their family and I'm not included. am I overreacting from pregnancy hormones or is this inappropriate or weird? do I have a right to be offended and angry? my fiance feels that maybe she just wants time with her kids but I'm supposed to be family and I'm your son's wife so aren't I family as well? any comments would be appreciated