Confused about a girl. Please Help!!!!!

Hi, I am an average looking guy. I really like this girl in my office. She is also an average looking girl. We've never actually spoken to each other. However, this girl knows that I really like her. Initially by her actions I felt that she also likes me as she always kept looking at me. Every time I looked at her I noticed that she is looking at me. Whenever she passes by my desk with her friend they would talk slowly and laugh. Also when I am around her she will do something to get my attention (like if she is talking on the phone, she will increase pitch of her voice).
I couldn't gather courage to ask her out and 6 months went away. Recently I felt that she have started mocking me with her friends. She and all her friends will smile at me in an very funny manner, which was really annoying. Once I was so much irritated that I gave a very bad comment about her weight (indirectly), as she is a little skinny. However later on I realized that I had been a jerk. I thought about apologizing to her. I was looking for the opportunity when she can be approached and I can apologize.

One day I was in the elevator and she also came inside with her friends. She starting to talk to her friends about how much she likes tall guys(I am not that tall, but taller than her). It was quite evident from her tone that she was pointing me. I really felt bad & rejected, but I did not reacted at that time and smiled away.
After that day I have started to ignore her every action. I have also changed my desk, since my desk is near office exit gate, and she often passes by. I don't go to cafeteria when she is there. I am avoiding her wherever possible.

A friend of mine who knows all this told me that every time she passes by my working area she tries to looks for me. Even I have noticed that. But when she is aware that i am looking at her, she would act as if she has not noticed me. Once she even changed her way intentionally when she saw me coming. Sometimes when I am passing by her work area, she will raise to check me out. But when she is with her friends it seems that she is mocking me. Even when she is not with her friends, they will smile at me in a funny manner.

I am really confused. I can’t understand what this girl wants. Neither I have any clue what I am supposed to do.

Should I move on or should I give 1 more try.
Please advice.

Please friends advice something

Dude this is what you do......send her a nice small bouquet of flowers (never over do it and buy expensive ones). send it with a card saying "you look so lovely today" signed your secret admirer (don't reveal who you are just yet). A romantic gesture like this will flatter her and get her excited. Do this a few more times over a few weeks, maybe send some sweets too, then show up at work with a red rose and ask her out.

I dont get why youd insult a girl you "really like" by calling her "average.. "

Anyway just ask her out

If you like a girl, you should just ask her out. There is no use wasting time to try to figure out what is on her mind. Trust me, no one will know the answer until you ask her yourself. Btw, a piece of advice, don't insult the girls you like unless you want to ruin your chances of making her your girl friend.