What was your last response? What will it be if she texts you again? Do you feel uncomfortable communicating your boundaries (values)?
My response was to change the subject and getting ourselves updated on our cats' lives

She can text me any time she wants. I will chat with her just like I would chat with any other female I know and have no romantic interest in. She begged to be friends at the end. Cool, we are. Well, more like very very distant acquaintances that exchange a few texts from time to time. It will never be like what it was, you can't fix or undo what was done. What she said last time was borderline (no pun intended) acceptable. Now if she open text tells me "when can you come visit me?" or "when can I visit you?" or something along those lines, that's when I have no choice but to bring up her fiance and tell her that, um, thanks but no thanks.