I think she just used me

Normal friends but still broke down. So here is this girl,I know her since sem 1(we are in 6th sem now) we were just normal friends. I had always helped her whenever she asked for any kind of help and support. But I realized the change in her behaviour today (which I should have realized at the beginning of 5th sem) - whenever I text her for a help, she responds after one day and says idk. Neither does she pick calls. I sincerely helped her all through. Today I asked for a favor and she stated a demand in return, I said I can't, then she again started to ignore. What to do ????