What does it mean when a girl kisses me on the lips for good luck?

A couple weeks ago I had a evaluation interview with the Air Force Academy and I told this girl who I've been seeing since March and I really like her (she also kisses me on the cheek and one time kissed me on my neck when she was gone for four weeks and we saw each other again) so when I told her I said she should give me something for good luck and she said she'll think about it and before I left she hugged me and said "aaaaaand" then kissed me on the lips and said "good luck" then last week I guess I was being flirty and I was just rubbing her arm all the way down to her hand then she grabbed my hand and just smiled at me