What did she mean by "lets be friends first"?

Any advice and opinions you have would be greatly appreciated.

Last night I finally got courage to tell the girl I like that I was interested in her. And her response was "I don't know, lets be friends first." But the thing is I've spent a large portion of the last quarter tutoring/studying with her and have even gone out to lunch/dinner with her and her friends. Which made me believe that we were already friends. And to make sure what she was I was on the same page as her I asked iff she meant that she wanted to hang out as friends more and get to know each other better first? To which she replied, "Yes".

Was she just being nice and trying to let me down easy without an outright rejection? Or is there a chance that she really does want to get to know me better first? What do you all think? And any advice on how to find out or determine which it is?
What did she mean by "lets be friends first"?
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