Sorry for the long post, but this girl is tough to read and most of the standard IoIs (flirting, kino, strong eye contact, standing close) don't really apply to her.
So there's this HB7 in a new social circle of mine, and she has been giving IoIs, but I know that she's also a big flirt and gives a lot of guys IoIs. I could be wrong, but I don't think she sleeps around. She seems to just enjoy flirting and getting to know people. I don't want to ostracize myself from the circle or make it awkward, so I want to be pretty sure she's interested before I do anything very overt.
My strategy up to this point has been to slowly escalate kino, try to isolate while still in proximity to the group, and not fawn over her / constantly try to interact with her like every guy she seems to encounter. It's probably worth noting that I'm not much of a flirt, and while I talk to other girls in the circle I don't flirt with them nor with HB7 while we're in a group.
The other night I escalated to being somewhat overt with kino and flirting and she seemed to respond well, but she made it pretty clear she wanted to walk home when her friend did. Her friend was probably within range of us to notice we were flirting in a more sexual manner than normal friendly flirting, and a couple days later she made a sexual reference to the two of us while we were both present and HB7 played along. Later that day, a guy who is good friends with HB7 asked playfully whether I was interested in anyone in the circle (the context was right so that it didn't seem like a pointed question).
IoIs that she gives that I don't think she gives to other guys, but it's possible I just don't see it: She often makes a point of saying hi with a really big, warm smile. I catch her looking at me especially when I'm laughing, she also sometimes glances at me quickly after she makes a joke. She also laughs at almost every joke I make, including the ones that are pretty bad.
She hasn't rejected any of my escalations (granted it hasn't been anything more than sitting cheek to cheek with a hand on her back), and she plays along, but she also hasn't taken the opportunity to be one-on-one with me when the opportunity has been there.
I've known her a few weeks now, and I'm not really sure where to go from here. Do I just keep trying to isolate when the timing is right (after a party etc) and continue to escalate kino/flirting until she rejects? Anything specific I should try?