[Rivière]

I've been in a situation similar to that, where a friend seems to give me all the signs in the world that indicate that there was more to our friendship than what it currently was. The thing was, it was just her genuinely being friendly because she was that comfortable with me. I cleared things up by asking her a few subtle questions without being too direct (since that can be quite awkward even for a close friend) and that was when I found she was just being friendly with me.

You could consider doing similar, such as pass comments about how she's behaving in X way towards you, but Y way to her boyfriend. I'd also point out to her that in one instance, her boyfriend has stated that he feels jealous of the interaction she has with you as opposed to him.

All in all, despite her actions towards you, for all you know, maybe you just make her feel safe? There doesn't always have to be something more to such gestures as those you've described, but you won't know if there is until you try and find a way to talk to her about her behaviour and find out more.