It means she wants to get to know you better, and she is not promising to be your girlfriend.
You say you "asked her out". What did you mean? Were you asking her on a date, or to be your girlfriend? So many high school kids are confused about the difference between casual dating and boyfriend/girlfriend. It is OKAY to date her casually while getting to know her. This means you go out on a date now and then without being boyfriend/girlfriend. It is also okay to date OTHER girls while getting to know her. Eventually if you like each other enough, you can progress to the boyfriend/girlfriend stage, and at that point it would not be appropriate to casually date other girls.
Just keep being nice, and ask her if she wants to catch a movie or basketball game sometime...
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?