Search Results: flirting while engaged

We have been co-workers for aout 5 years now. Friends for maybe half of that. Not super close and we don't usually get all deep in our conversations. I honestly never had a "thing" for her. Once in a while she may be wearing something that looked really hot, and I would notice.
She has a boyfriend. Actually, they are engaged. She told me back when it happened she felt kind of put on the spot and is not sure if she will actually go all the way and marry him. She loves him, but there are issues. About a year ago she started flirting heavy with me while drunk. I stopped her. Otherwise there is some sexual innuendo here and there, like most friends have. Until recently. She was home alone and wanted to hang out, which is not not common, but not unusual either. She wanted to have some drinks, eat something, watch some movies and talk. Everything went as usual. I went to bed in the guest room and fell asleep. About an hour passes and I wake up to someone getting into my bed. It was her. She snuggled up to me and I assumed she just didn't want to sleep alone, so I put my arm around her and started to go back to sleep. She took my hand and put it between her legs. One thing led to another and all lines were crossed. It actually was very good sex. Somehow I already knew my way around her body, like I had been with her 100 times before.
The next day I wake up and she is downstairs cooking breakfast and her boyfriend is home. He thanked me for keeping her company. I felt bad knowing what had happened. I never mentioned it, just went on like usual. A week passed and she brought it up. Ever since the sexual innuendo is off the charts. She finds ways to use it in everything we say. She is looking for excuses to have me over, like helping her fix stuff around the house. Today after work she texted me she bought me a gift (no idea what it is). Is she lining me up as a replacement? Or a fuck buddy to get her through her relationship? Or was it a one time mistake she feels bad for?

On Saturday i girl that i was looking at came up to me while playing pool with my friend and brother and she made sure i was on her team and she was a really lovely girl and i liked her and she liked me a lot but she told me that she was engaged to someone else for a year but she kept playing with her ring and wanting off and she said if it wasn't for the fact she was engaged to her bf then she would be mine.
and we continued getting know each other and we went to a club and we danced and played more pool and then she was flirting and holding my hand and i wanted kiss her but knew she was engaged. but the questions i keep asking myself are
1. do i keep pursuing her?
2. is cheating because i am single but she engaged?
3 . do i just be her friend?
4. do i leave her alone and do nothing?
5. do i let marry this guy because i really like her?