is my coworker flirting with me??

maybe not entirely. keep in mind you've had this connection/flirt for quite a while now and if she wants the same as you she's used to nothing happening, used to false alarm and so on. In one way you were clear but also rather subtle. you didn't reveal your intentions clear enough after this long relationship. She could have interpreted it as a friendly gesture.

Friends give necklaces, too. My female friends have given me beautiful pieces of jewelry as gifts.

Unless it was obvious that you spent a lot of money on it, or went to some very special place to get it just for her: the message is still vague.

She will probably get that you like her as a person. The gift was lovely; and she knows you were thinking of her and went out of your way to get her something.

have fun.

I agree with UT and itsallgrand, she probably still doesn't know what your intentions are. This flirting and eye contact thing has been going on a long time and the two of you haven't ever spent time together outside of work. Unless it was obvious that you spent a lot of money on the necklace or made it yourself then she might just think of it as a friendly gesture.

I really think you want something to happen. All you have to do is ask her to coffee.

This is better than any chick flick, except it's keeping me in suspense too long!