At the time I asked my co-worker out (I'm not anymore) I had been texting her and we even hanged outside of work to a movie with a few friends. I asked her out a few weeks later and she said sorry she's to busy and doesn't date co-workers. Took a break from texting her. Then I tested her again and when we did it was for the rest of the day. I asked to see if wanted to hang out a few times, but says already has plans or is working. Should I try keep texting her or is she not interested?
Sorry she's just not interested. Busy and don't date coworkers...those are standard excuses. Obviously she has time for friends and stuff...if she wanted you to be one of then you'd know. Why she hung out with you and led you on, I don't know. That's lame.
She's not interested. Look closely at what she said, "Doesn't date co-workers". This is a fact that you can't change.
Does she only reject you for these dates, but continues to hang out with you casually or with friends? If the answer is yes, then it's definite that she's not interested in you romantically, but doesn't want to spoil the friendship with you.
If both of you don't hang out together with friends after both of you are no longer coworkers, then that means she might doesn't want to burn bridges; you are just a good networking reference.
Don't push it. Continue whatever seems to be working, but don't wait for her. Until she is willing to make the next move, you are not going to get anywhere, so better focus your life doing what you like, and stop obsessing over her.