Did it ever occur to you that she may just be busy? I mean, her mom is in town and she could spending time with her, or its just a busy time for her. Maybe thats why she changed her schedule too, to accommodate for something else. You can still save this, just lay back for about a week. Don't feel pressured you have to talk to her every day, even though there is that other guy, you two work at the same place and will eventually run into each other. So for now, calm down, or else things are going to get from bad to worse. Just hold off from calling her and talk to her in person.

Next time you see her, gauge her response, and DON'T THINK/FEEL NEGATIVE. From an objective stand point see if she is trying to avoid you: is she avoid eye contact, less talktive than usual, etc. And if you feel that there is something wrong, like she is purposely ignoring you, when you have a break or after work, ask her whats wrong. She will either just not say anything and just ignore, if she does, they you lose. Hopefully she will say 'nothing' (the word, not silence). If she does, ask her again, she will probably say 'nothing' again. Ask her up to 3 times, and even use your friendship as reason for her to talk to you. This is tip-toeing on the 'friendzone' but you can repair it by offering her a night on the town to cheer her up, after she explains her problem, which shouldn't be related to you.

If it is you, try to explain yourself, be honest, but don't tell her you love her, thats relationship suicide. Just say 'you are an awesome person to be with...when I see you my day seems better...the reason why I tried to contact you some many times is because I wanted to know if it was you are just coincidence or really you...' I really don't know, because I never want to be put into that situation. But it shouldn't come down to that.

By the way you have a msn? I feel like I am always too late with advice.