what youre experiencing is a form of buyers remorse - where she has gone too far too fast with you, and isnt comfortable enough to keep going at that pace.
people fall into patterns of behaviour - in her mind repeatedly seeing you at night for a coffee or dinner qualifies as a "date", many "dates" in a row qualifies as "seeing someone", then "seeing someone" exclusively for a long time (more than a couple weeks) plus sex qualifies as "a relationship" and thats whats setting off a bunch of issues in her mind ie "omg, im out of a relationship with 'brad' and now ive replaced him with 'yarg' and is he good enough and is brad better and did i do the right hting and is he a rebound and am i a slut what does he expect what if he falls for me too hard and i cant get rid of him and is this what i really really want and i still kind of miss brad and omgomgomgomgomgomg"
its a bit like mental dominoes. one thought/image trips off a cascade of thoughts taht end up with a person experiencing an emotional event. what you need to do is avoid tripping off that little cascade.
what you need to do is defuse the situation, and make all the issues non issues.
the standard position i come from when im getting with a girl saying what yours is saying is to say something like:
"hey. i like hanging with you. youre cool. i relax, i have fun, youre nice to talk to, youre ocasionally funny but not as funny as me, which isnt your fault coz im the best, and if you keep up with all this 'what does this mean what is our relationship where are we going' bullshit its going to suck the fun out of how we talk to each other and im going to stop talking to you, coz i dont hang with people who arent fun. youre jsut out of a relationship. im not dating you, coz youre a nutjob at the moment and anyone would be crazy to actually date you until you get over your mental problems, but thats ok- when i see your name in my phone i get a nice feeling, i buzz you, we hang, and we enjoy each others company. sometimes i let you have sex with me coz you chicks have needs, and you go mental if you dont feel like someone wants you now and again. so, its quite simple: do you like hanging out with me as well? if not, cool, go hang with your mum/sis/cuz/a random/whatever, and stop giving me a headache. if you do like hanging with me, then shush, lets go get some bad food and a movie"
anything she says after that, cut her off and ask "yes you have fun or no you dont. the end. i dont want to think about it. pick one."
saying the above allows her to rationalise going out with you/hanging with you/sexing with you WITHOUT going down the "omg hes my new bf what about brad omgomgomg" path. its embedded with the idea that youre a fun, socially intelligent guy who doesnt fall into problematic behaviour (thingking that youre her bf before you really are) and your willingness to tell her to go away also increases your value in her eyes, keeping her attracted/intrigued.
step out of the "boy meets girl, boy fucks girl, boy must have girl exclusively" mindset.
you are a really social guy. you are really cool to hang with. you have sex because it feels good, not to mark your territory and brag, like normal male behaviour. you have lots of options. you are fun. if she doesnt see it, then frankly, shes too stupid/uncool to hang with, thank her for cutting herself, and her bullshit, out of your life, coz there are 100000 other women who are after exactly what youve got.
if you come to believe that last paragraph, you will have a cloud of women in your life all the time, and they WILL accumulate to the point where you have to start choosing one over the other, because there isnt enough time to eat/sleep/work/train AND date all of them.
come to think of it, i actually got rid of one last night. young chicks, mang. theyre fun and look great, but some of the stuff they try to pull really pisses you off
oh.