Don’t believe that you are devalued. Just because she doesn’t feel the same way about you, that has no bearing on your value. People can’t help loving who they love or being attracted to who they are attracted to (even if it appears that they are attracted to the wrong people) and you can’t force somebody to love you.
If you are still friendly enough with this woman that you can talk to her, rationally, without getting all choked up. Just ask her if she wouldn’t mind talking about her new love interests in front of you, because it makes you feel like crap. I’m assuming that she knows that you were interested in her and she told you that she didn’t feel the same way, right? If you had a secret crush on her, I wouldn’t speak up to ask her to stop talking about her conquests or then she’ll find out about your crush.
In the meantime, if you can avoid her at work, do so without appearing to be obvious. Don’t seek her out. If you have to have regular contact with her, just be cordial and polite, but don’t engage her in conversation and don’t let her rope you into a conversation.
Then, figure out what you are really looking for in a relationship and ask your friends (outside of work) to help you out with finding someone else to date that will be a better match for you. You might have to date a few or a lot of people to find the right person for you.
When you find yourself starting to pine over this woman at work, come up with some little thing, whether it’s a mantra, or coming up with an image of a beautiful nature scene, or think of a funny line from a movie that you like and then conjer it up, whenever you start to feel crappy about this woman. Don’t allow the thoughts of her to invade your mind, push them out with your “new thing” whatever it is that you choose. Even if you have to do it over and over again for awhile.
When you’re at home and you start to think about her, have a list of actions that you will take instead of thinking about her. Call your best friend and talk about sports, go for a walk in the park, make a list of home repairs, grocery list, foods you’d like to try, gifts you need to buy for this year’s upcoming holidays, places that you would like to travel to. Just do something (productive) instead of thinking about her.