She's using you as a second string boyfriend. She wants all the attention a boyfriend would give her without having to be your girlfriend. I've had this happen to me before.
Push her into the LJBF zone explicitly before she implicitly eases you into it. Don't call her - wait for her to call you.
Don't invite her over. Wait for her to ask if she can come. The next time you sleep in a bed together be very uncomfortable. Don't cuddle with her and look as distant as possible. She'll probably ask you what's wrong.
Tell her you've been thinking and have come to the conclusion that it's best if you two are just friends and don't do the whole sleeping over thing.
Now she'll probably ask you why you've come to this conclusion. At this point I'm just making shit up and I don't know how well it will work so use it at your own risk. You could say - "Well, I've been reading about all these different ways to make a girl orgasm and I really want to try them out."
I could anticipate her saying "well why don't you try them out on me?". Your response should be, "why don't you make me".
Here she will probably get pissed off and leave, or she'll jump on you like there's no tomorrow. Either way you're out of the LJBF zone.
Also see this link to learn some cool new stuff so you'll be telling the truth.
stacking-orgasms-how-to-do-it-vt20393.h ... quins+kiss
Goodluck and let us know how it goes
CPT