Yeah, totally WTF. Sure, great relationships can start at work, but the really big glaring thing I see missing from this letter is any indication that there's reciprocal feelings rather than it being entirely LW's pantsfeels. And, yanno, beyond that, it's really dangerous territory to start up a relationship with someone you work closely with, simply because of power dynamics and bringing the personal distractions into professional productivity. From what LW says, it's pretty clear to me that they have some amount of informal power over the coworker, even if it's not managerial ("I was trying to show her the job," and "I’ve been there a year longer so am further up on pay scale"). So no, don't go there.