Mother in law with rude comments

So my mother in law has always been saying how we're spending all this time and money on this wedding when we should be having a baby. Wich my fiancé and I always said we don't want any kids until after we are married. We want to get married and enjoy our marriage. So she has always made rude comments about us not having kids. Last night we were at a family party and she had made a rude comment like " my son has yet given me a grandchild, I want one now even if I have to get him with a prostitute I will get my grandchild" my fiancé and I both were really upset even my father inlaw had to tell her to stop. I just don't know what to do. This is my mother in law and she is just to much. Another event she had offered me wine at a family event and she put salt in my wine cup I was so confused didn't think anything of it but then I asked every who had the wine if they found anything strange in there wine and they didn't. I showed my fiancé and he said yea there is definitely salt in your cup