the same person keeps getting access to my account, but it does not show up on my phone how do i stop her from getting my my account

I have changed my password about 20 times in the last two month, yet still the same girl in California (i live in another state) keeps getting into my account. She is paying for apps at the moment with her own card but, she is always stopping me from listen to my apple music and i keep getting emails about apps that she has bought. apple claims there is nothing that can be done besides changing my password yet here i am still with the problem 20 password changes later what the heck am i supposed to do. no i have never even met this girl, but i do have her debit card info and mom address now.