So according to MM’s interpretation, young unmarried girls do not get olam haba, career women do not get olam haba, etc. etc–no matter what else they do in their lives, no matter how many mitzvot they perform. Of course this directly contradicts the Mishna that I quoted above. Unless, of course, MM thinks that “Kol Yisrael yesh lahem chelek l’olam haba” does not include women.
It is so easy to latch on to a single phrase from the Gemara, one which makes a suggestion on how a woman can merit olam haba, and decide that this is the only way–simply because it is the only way mentioned. (Actually, I do not know if this is really the only way mentioned; I have not learned all of Shas.)