Should I apologise to this girl and talk to her again ? Is what I'm doing to her childish ? Should I speak to her or just ignore her ? Help?

I'm 21 years old male. There is this girl in my office . She has a boyfriend but she talks to guys in the office. Her boyfriend is not in office. But we are kind of friends according to me but she never approaches and it's always me approaching her . Even when I go and sit next to her , she never makes eye contact with me and only occasionally makes it .I joke around a lot with her and also pull her out of the lift while leaving office. It hurt her hand twice when I did that . She looks at me when I'm talking but not looking at her.I keep approaching her thinking that I'm her friend so it's fine .But I think she is taking my friendship for granted . She makes eye contact with other people. If I don't approach her she will never care that I didn't talk to her. This one sided friendship won't work for me and this makes me depressed everyday when I'm going home. I don't have feelings for her but it's just the friendship thing . The next day I ignored her completely and she approached me 3 times but I ignored her and the last time she had approached me she said that I will regret this . I told I will never. And after that when I was leaving office , she scremed bye !! But I still ignored her and next day we both ignored each other but I wasn't feeling well and so I was leaving office early and she called out my name but I ignored. I am very hurt because in the past I always approached her . The other day she tried giving me five when we won a game but I ignored. Is this childish?