Why does she says Idk?

Well, there is a girl in my school that I like her and it is been almost a year that I know her, I talk to her 2 or 3 days a week about 3 minutes ( we don't have any classes together) two weeks ago I told her that " I like you and I wanna spend more time with you." ( she was smiling all the time ) and she said " same" then about two days ago I asked " would like to hang out with me?" She said " Idk" then I asked " do u even wanna hang out with me or not?" She said " I don't know " again.
Guys and especially girls can you help me please? I don't know what should I do and what does she mean by that?
Why does she says Idk?
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