Hi phillk!
I agree with the other post in that if this person is a lateral co-worker then I would not put any stock in what she has to say...especially in regard to your self-worth. In fact, I would go so far as to say that quite possibly she is certainly trying to make you second guess yourself and your abilities in order to make herself feel and/or appear to be a more competent employee.
The truth is - we can only control ourselves...and we do control our responses and reactions. She cannot make you feel any way that you do not allow her to do to you. Youknow your skill levels and you abilities...don't allow her to try and make you doubt yourself.
As for bringing it up to the boss, well, that's a sticky situation. I can totally see why you would want to, but we have to be so careful at work about perceptions, etc. If it were me (and I TOTALLY don't know what your work culture/environment are like, so this is purely speculative....you'll have to make this call yourself!) I would not bring it up to the boss for several reasons: (1) don't want to even put that idea (you co-worker's opinion) in his/her head...like your boss might think later on..."Well, I wonder if Ms. ___ is right about that?"...kind of thing. (2) Don't want to appear that I'm "wasting time" dwelling over a non-issue when I could be doing my work well and therefore proving her wrong. (3) Give your coworker enough rope...it will start being obvious that she is a negative, complainer instead of a productive team-player...it's one of those "if you're not part of the solution, then you must be part of the problem" kind of things. (4) Not giving any visible credit to what she has said will just reinforce to her that you don't put any credit in her opinion...you have given her no power over you...and frankly, what she says really doesn't matter. (5) You never want to go in a boss's office to present a problem without having a solution...if you want to tell your boss, make sure you have some options for how to fix this situation (ie - "My goal is to see this project to completion in the most cost-effective, efficient manner possible. I might not have all the answers, but that is why team work is so essential to what we are doing. I am just not getting that sense of team effort from her [co-worker]. Perhaps the project would progress at a more productive pace if she handled X-aspect of it and I handled Y-aspect"...something like that...).
Having been in the workforce for 25+ years (OMG - has it been THAT long?!?!?

) I've seen a LOT of office interactions like this. The truth usually comes out...or I've realized that better employment was ELSEWHERE!
If you really want to say something to your coworker, to stand up to her so to speak, whatever you do...DO NOT REACT! Take deep breaths like on the relaxation tape...think about what she has said and the truth behind it. If there is no truth to what she said...decide IF you want to react to her at all. She does NOT control you...do NOT give her that power!
And one more thing (while I'm on a roll

), if you do make a mistake (don't we all? Uh...yeah...we do!:)) or a bad decision, so what? Own up to it and fix it. I know that is easier said than done sometimes, but most bosses appreciate a direct acknowledgement, responsibility, and solution suggestions.
Best wishes, phil! You can do this!!!
Best,
Dawn