Ein Masiin sefakos al pi hanashim

I really have trouble understanding that statement. We know that by isur v'heter we do rely on women as much men. It's only with regard to eidus that we don't rely on them. Is this statement exclusive to women or does it really mean al pi eid echad (no difference if it's a man or woman)? This clearly isn't real eidus so why shouldn't we rely on them? Someone suggested that it could be since it could lead to something serious like the girl being killed if was over on a chiyuv misa but that still seems strange to me. Any time that we rely on eid echad it could eventually lead to some kind of eidus.

The Ritva explains that it's not because of aidus but because an eid echad isn't believed by a davar sheb'erva. So according to him it's clear that it doesn't make a difference it's a man or lady just that it's not two kasher eidim. He then says that the reason we do believe them in some of these cases because it's milsa d'avida l'agluya. It could become obvious if they're lying so we can assume that they're telling the truth.

I think that I still don't understand all the details and maybe I'll have a chance to look at other stuff over Shabbos or later today.