What should I do when I invite a girl to something and she doesn't know?

I invited this girl to an upcoming concert. It's for 4 days, so she can go any day she wants. But when I told her that, she still said she doesn't know. I already got the sign that she's not too keen with going. I don't really mind if she doesn't want to go as long as she's honest about it, but still, what should I do?
What should I do when I invite a girl to something and she doesn't know?
Call her up and give her an "out", tell her you still want her to go, but if she can't make it then you have someone else who REALLY wants to go. If she says she is still interested then ask her for a specific day as you have arrangement s to make. One way or another you will find out.
Reply:ask her again if shes going then say if you dont wanna then just tell me and go from there