Bro, I seriously doubt you've given us the whole story. But thats o.k., you're not defeated until you admit it. You can still win, but it's going to take some work. First and foremost, learn from her. You hate to be treated this way, so don't ever act like her.
From now on, you should make every woman feel like the most beautiful woman on the face of the planet. That doesn't mean hit on them, but make them feel appreciated. Just try to be sincere about it, it'll make you a better person. Chicks dig better people.
The second rule is, and this is the most important one, you must never, never, settle for dating under your standards. We have the bad habit of hooking up with a chick just because she's drunk, and it's getting late. Do not fall into this bad habit. Remember, those that need it the least, get it the most, and those that need it the most, get it the least. This rule applies to business as well and will serve you well in later life. Once you are seen with the finest girl you know on your arm, tell her to run along and wait for the rest of them.
This tramp at work will come around. She'll see you with Jenny Pom-Pom, and wonder what she's missing out on. She'll ask the chicks at the office, and they'll tell her how sensetive you are, and remember their birthdays. Yeah, she'll come around. And then you strike. The day you set a date with her and you're sure about getting her in the sac, eat a family size can of beans and lay some wolf bait on her while she's slobbing your nob! And them you give her the dirty Sanches-where your hitting it doggy style and run your fingers up your ass and then hold her face with that hand and let her try to get away!
The best part is, nobody will ever believe her!