Does sending short text mean a girl is not interested?

I've been texting her for a few days, and ill send a sentence or two and she'll reply back, "you're too sweet" or "awww thanks :)". I was talking to her on facebook and she was sending longer messages so its just when she texts? She's really nice and cool and I think I like her, I just want to continue talking to her without bothering her or getting on her nerves. she usually sends a smiley face after everything, but the messages are short lol. I know I'm making too big of a deal over this, but I'm usually the kind of person that always replys back to anything.