Re: Why is she acting this way
Don't be this chicks emotional escape from the relationship.
we would text nearly everyday up until November
She might not be getting attention from him and you're giving it to her. Unfortunately you're not getting anything in return. This is NOT how texting works. Anything could of went wrong there. You may have been responding too quickly, or failing to amp up the tension. I would suggest reading material on texting in this forum (read the stickies).
Use your personal interaction to an advantage. Lots of kino would've worked there. She showed immense attraction to ask for your number. By touching her, you'd be giving her a taste of what's to come. If you're still working with the girl, do it and see how she responds. Come up behind her and touch her arm "Hey you're working tonight?". If she's challenging you or being sassy/flirty pinch her arm very lightly.
This is needy on your part. Don't do this. Clearly it's just her lack of interest. You need to find a way to escalate again. Be spontaneous say "OMG you'll never guess what just happened" wait for a response, then reference something you saw that reminds you of a fun time you two had at work.
i called her out and asked why she doesnt talk anymore
This would be a little better:
U "You must've been in jail last week"
U "You stopped texting so I thought I'd have to come bail you out."
Get her our for coffee after work. Don't mention the boyfriend. He doesn't exist in your mind. Although if she's mentioning him, it's a bad sign.
For whatever reason, she's getting disinterest. Think about some tendencies you have to put her on a pedestal or be needy and try to figure out how you can make yourself be the prize.
Discovering PUA one step at a time.
Feel free to disagree with my opinions. I encourage it!