Yeah, my ex girlfriend had a habit of being like the last option to her male friends. She was always flirty enough that she had plausible deniability, but dudes could read into it and think "she likes me."
I saw this recently with an ex. I was an idiot and wanted her back a bit (crazy hot and super high libido. yes I'm still blue pilled in actions). She wasn't that keen given when I dumped her, I also got some revenge on her for cheating.
I think this is a really good post. If you want to have causal relationships, you need to be somewhat disengaged. She's in a casual relationship because she doesn't want drama, she just wants simple fun.