I have a pretty co-worker and the moment she started working at the office I had my eyes on her, I did not approach immediately and maybe started to engage with her a couple of months later. We had fun small interactions and I started noticing a lot of things in common with her.

2 months ago, I asked her out and we went on a date, we went for wine and spent about 3 hours just talking and listening to each other. It was after the first hour that I noticed my interest in her grew and I wanted a relationship with her.

I also noticed that there was someone really close to her at the office as they were classmates in college. 

I went out one more time with her at happy hour with workmates and the chemistry was obvious. I tried stealing a kiss couple of times but only ended with kiss on the cheek.

I started developing feelings for her and tried to go more with her but she kept postponing. The chemistry in the office was still there and we had lots of deep conversations. But also very sexual and flirty.

I asked her out one more time and she told me was already seeing someone. I told her that I wanted a relationship with her and that she let me know if that doesn't work out. She was surprised and told me she thought I only wanted to fuck her. I told her yes that was my intention at first but that I saw something else on her, but I still want to fuck her.

We laughed and flirting continues for a couple of weeks, now I have confirmed that the person she is seeing is the close friend also a coworker. I ignore the fact and keep flirting and telling her that we should be together, and she says she wants to do things right and that she can't be with me. She doesn't deny the chemistry and that we have a lot in common but she thinks that we are too alike to be together.

I kept flirting with her and making sexual comments but at the same time compliments and some romantic details. I kept teasing her and she somehow responded. 

Yesterday she saw me with another pretty co-worker having coffee, and later in the night I saw she blocked me on Whatsapp and today she was all cold.

I should mention she is hot and somehow an introvert, I'm a skinny guy but I'm pretty social active, practice skydiving and really successful senior engineer. The other guy is a junior as so is she.

I know I entered the friend zone, and that maybe she used me to make the other guy jealous. But would like your opinion.

Should I just ignore her and hope she grows interest on me again or just forget about her?