I know it's too late, but maybe this can help you out for the future.
First, your text "well we could still go out on a date and have a good time without being in a relationship. I'm not trying to force you into anything, i just wanted to see where i stand and now i know", I would cut the last bit, it's too long and too much of an explanation. Remember that you aren't supposed to care so much about if you are with her or not, because I think that with what you said, it looks even more serious. It's like, "this is not serious but...", so then it looks serious. Also remember that you don't want to date her, you just want to hang out with her. So something like "That's fine with me, we should hang out and have a good time on day X. I don't want anything serious neither, just want to get to know you better".
The whole thing looks much like you opened right and then behave like a nice guy, which would put you in the friends zone, but you didn't build enough emotional and physical attraction. (Step C2 in the M3 from Mystery).
Other point, why do you know she was in a long relationship? You shouldn't know as you shouldn't talk about past relationships.
How to fix it? As I said now it's surely too late, but if this happened again, I'd say to carefully introduce sexual jokes, double senses and to heat up the talk, being between the "Nice guy" that she already thinks you are and being careful not to be too much "not like you". It'd be easier to try a new one anyway.