I have found myself in this situation a couple times and I don't know how to work my way through it.

Situation: I am with a group of friends at the bar, one of the girls in the group is flirting heavily with me. She invites me to an after party at her house which is only a couple of people and quickly dies down. At some point it is just me and her and one other couple making out on the other side of the room. I put my arm around her and she's receptive but otherwise not showing much interest in physical escalation. From one perspective it seems insanely obvious: she invites me back to her place, we are basically alone on the couch with my arm around her but every time I hint towards a kiss she gets awkward and backs out. She keeps saying she "should probably go to bed" but she's not, she gets another drink and sits back down on the couch with me. All the signs are pointing toward interest but when I try to escalate (even just a kiss) she backs out and gets weird about it.

it seems clear that she is interested but hesitant and needs a slight amount of convincing. The idea of "convincing" or "pressure" sounds weird/bad on the surface but we all know we have been in the situation where a girl has given you all the right signals to the point where you are alone at her place but she still puts up resistance/rejection when you try to make a move (again I want to stress this is just kissing, let's forget sex for the moment). How do you talk through this and escalate without coming across as pushy but also not coming across as weak or timid?