Future mother-in-law mad that my mom likes my fiance's stepmom better than her. Isn't that petty?

Neither my mom or myself care for my FMIL, but we both love FH's stepmom or "bonus mom" to death. Both my mom and I have more in common with FH's bonus mom than with FMIL, who we find to be rude, push and extremely nosy. FMIL has asked my mom out to lunch and to other activities several times and my mom has always politely declined (often citing her busy schedule-she is a judge) and each time my mom says no, FMIL goes to FH and whines like a 3 year old about my mom hurting my feelings. FMIL mainly does not like how my mom has gone out with FH's bonus mom several times and had her over to her and my dad's house-which FMIL has not been invited to. FMIL is also upset because she came over to the place FH and I share unexpectedly and was mad to see FH's bonus mom, me and my mom cooking in the kitchen and having a good time. FMIL told FH that "we had no right" to do anything "without her" and that it was "wrong" of me and my mom to ociate with his bonus mom. First of all, my mom and I can ociate with who we want. We owe nothing to FMIL nor does she need an explanation as to who we spend our time with. FMIL is an obnoxious woman who once made fun of FH's grandmother-her own mother-in-law, at a family dinner, saying FH's grandmother's dentures "whistled" when she talked. I was at that dinner and because of that incident, I find it hard to respect the woman. By hte way, FH's bonus mom was not the "other woman"-FH's dad remarried 6 years after he divorced FMIL. Why would FH's mom think either mom or myself would want to be around her?