Shall I tell her?

first of all i am new to this so thanks for reading and helping me with my dilemma. I started talking to this girl at the start of the year who works for a company where we order our parts from for work. She is my contact so i speak to her everyday regarding what parts I need, its a bit like a 'Gavin and Stacey' situation. Anyway I thought i'd search for her on facebook as we were getting quite friendly, this was after 4 months of speaking. I added her on facebook and then basically we spoke pretty much everyday. if we weren't talking at work we would message each other on a night. Anyway i thought one night I'd look through her photos and she appeared to have quite alot of photos with the same guy, when i asked who this guy was it is her boyfriend. She has been going out with this guy two and a half years now and has just moved in with him. Once I found it she had a boyfriend i backed off completely because i thought that obviously this wasnt going to be anymore then just a friendship. But!!! she messages me everyday sometimes twice a day. if i dont message her after a few days she will send me a message saying: "hey, your quiet? everything ok?" this girl is driving me crazy!! we both have similar interests and we just understand each other. The dilemma I'm in is do i tell her that i want to be more then friends even though she has a boyfriend? i know your probably thinking 'well yeah' but i have to speak to this girl everyday so i don't want to tell her and it be very awkward from there on. if i didn't have to speak to her everyday I'd tell her. The thing is she is quite a shy and timid kind of girl so she isnt looking for attention or anything like that. Some of my friends think that she likes me but doesnt have the courage to dump her boyfriend. what does everyone think? the conclusion: we both speak everyday, i really like her. She has a boyfriend but do i tell her i like her? oh by the way we have never met either. Thanks guys much appreciated.

then why would she message me on facebook outside of work? she has already said a few times that we will have to meet up. "Find yourself a real live, in-the-flesh woman" - you make me sound like a right geek/nerd. I do go out every other week. i do talk to girls in the flesh ha. but yeah i think going to have to back off. because im not a nasty person ill just reply to her 'non work questions' once a week or something.