Some girl wants me to buy alcohol for her for something she is doing without me?

A girl I met online a few months ago and hung out a couple of times texted me and asked me if I could buy her alcohol before January 1st because she needed it. I asked her what she was doing and she said she had plans. Didn't invite me or nothing. What do you think I should do. She is 18 and in the US it is illegal for consumption and sales of a younger person below 21.
Some girl wants me to buy alcohol for her for something she is doing without me?
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