Note the gemara says that the woman performs certain serveices for her husband, but does not mention what happens if she doesn’t. We know there is a klal takinu mezonoseha tachas maiseh yadeha (outside work). If these things are considered maiseh yadeha although they are internal work, then the Rayvad makes a lot of sense. SInce she is reneging on the deal, we decrease her mezonos accordingly.
However, the source for the Rambam is shver. (Have not looked up the nosei keilim.) The mechaber or rama does bring somewhere that a woman who curses her husband’s parents can be hit. It seems that this is because she would be considered some kind of moredes. Maybe that would apply here as well, because of moredes. (I don’t know what the mechaber’s source is there either, since normally a moredes is just forced to get divorced, but is not given any corporal punishment.) I haven’t looked inside, so don’t rely on this. Need to check.