My three year old daughter suddenly refuses to go to her grandparents house. Should I make her go?

She used to always love to go. She would even cry when we picked her up. Now I am pregnant again and she will not go. They want me to make her come. But I don't want her to feel abandoned. I also feel they might have said something to her about the baby coming that made her insecure.My mother-in-law has no children(she is stepmom to my husband) & she is always saying things like give her to me or let her live with us. She tries to tell me she will be spoiled & bad if I don't make her go. They also tend to try & keep her longer than I say she can stay by going through my husband.Last time she went she told me that she wanted me but they wouldn't bring her home. I am really confused at what to do. I don't want to start a family problem, but I also know this is stressing out my little one & I am worried if I do the wrong thing I could hurt the bond I have with my child. I am the mother of 4 girls & one on the way & I have never had a problem like this.