Did i get shot down after sleeping with a girl?

ok i don't really have much dating experience so this is something that really confused me here is what happened i'm 21 there is this chick where i work who is 19 i have had my eye on her for awhile now (before anyone says anything i know dating someone i work with is a bad idea but nether of us plans on working there much longer i so i figured what the hell?) anyway a few weeks ago she invited me to spend the night at her place we weren't really that close like dating or anything and i didn't really believe she wanted sex so i assumed she meant sleeping on her couch or something anyway i said yes cause it was a great chance to spend more time with her and make a few moves anyway we go to bed that night and she tells me i'm sleeping i her bed so i decide this is as good a time as any to make my move but when i tried to kiss her she turned away and says now isn't a good time for her to be in a relationship i take this as the nice way of her saying i'm not interested this has since bugged me in the back of my mind and won't stop i can't figure out why she wanted to sleep with me but nothing more i never expected sex because i kinda thought she wanted to take things slow why did she want to sleep in the same bed as me if she didn't want to go out with me or even just one time sex me being the stubborn idiot i am i still asked her on a date not long after that and she said yes but i kept thinking about that night in the back of my mind and the whole thing felt awkward we haven't hung out since did i just make the wrong assumption or was i right and i screwed something up before i got anywhere i have asked all my friends what they think and they all give much different answers even though i am over the girl that night continues to bug the crap outta me