Here's some quick research I did of some of the women they replaced:
TALITA BERNARDO: 1-3 in UFC
TONYA EVINGER: 0-3 in UFC
RACHAEL OSTOVICH: 1-3 in UFC
LUCIE PUDILOVA: 2-5 in UFC
GINA MAZANY: 2-4 in UFC (left on a win which I guess is a little odd)
The UFC has a lot more leeway for women in terms of performances. Sure, they cut fighters like Romero but that has nothing to do with replacing fighters in the women division. I don't get how people see these signing and correlate that to "they couldn't keep Romero but they sign these fighters." Romero was bad for the division. They treated him like a king and have him so many chances to get gold yet he never pushed himself into the next gear to get the title. That and he kept losing technically and was getting paid well for it.