We never discussed what kind of relationship each other was looking for as well.
Most Helpful Girl
If you break it off now it she will feel like you used her for sex and she will also wonder if she did something wrong.
Having said that being in a relationship that you know is not going to work is only going to make you misserable and give her false hopes.
My advice and its only advice, is to talk to her and ask her what she is looking for in a relationship and talk about it, then say to her that what she is looking for is not what your looking for or even if your ready for a relationship.
Be honest with her, re assure her its not her,( if it's not) but better to sort it now than lead her on because if she falls for you, it's going to hurt more.
Hope this helps.
All the best.