People seem to be conflating the terms "sexy" and "sexualized." Which is honestly an easy mistake to make if all you see are the extremes of an argument.
I understand the point being made about Tali's changes in that it wasn't necessary to further exaggerate her hip-waist ratio. She already looked perfectly feminine.
That said, I agree with those above. I don't believe this counts as sexualization. Sexy? Yes. Being sexy is fine. Being modest is fine. Being anywhere in between is fine. Sexualization has less to do with how someone looks as how it's presented. Miranda in a catsuit? Sexy. Miranda's catsuited wedgie taking up half the screen in every conversation? Sexualization.
EDIT: Or at least, that's how I understand it. I may be wrong.
EDIT2: Because I want to make clear, someone fully clothed can be sexualized just as easily as someone wearing less. It works both ways. It's just that it's clothes + context (and in media, things like pose, camera angle, etc.), not clothes by themselves. To go swimming you should be able to wear a swimsuit without being accused of immodesty. Likewise, it's a terrible idea to go into a combat situation in high heels.