Is this odd for a fwb relationship?

So for some context. We've been acquaintances for awhile. She messaged me recently about being in an open relationship and basically extending a fwb relationship without her boyfriend being involved.

I've been in fwb situations but never with a poly relationship behind the girl.

Anyway, I've been getting off feelings about this being just a fwb relationship. First, she texts me constantly. Like, if I don't respond, I'll get 5 texts within an hour or two. I'm used to just contacting to meet up for sex/meet ups. She added me on Facebook. I generally keep my friends/fwb seperate. She specifically asked if it would be a one night stand or could we cuddle and other things too. She then asked recently if I would date her if she was single.

I clearly expressed being interested until I found an SO I wanted to date. Is it just me, or does she seem fairly clingy/not really typical fwb stuff?