Well, I am a lawyer, and I work in employment law, so let me second Otto’s excellent post. Check your company’s harassment policy–the first step will most likely be asking the harasser to stop, or, if you feel you cannot, telling her supervisor and asking the supervisor to talk to her. You seemed to have done this, if only informally. It is, as many have suggested, a good idea to document this, as well as the type of actions that are making you uncomfortable and the frequency of them. The policy should also tell you what your options are if the harrassment continues. Try to go through each of those steps–again documenting who you talked with and when, and any response. In addition to the EEOC, your State may have an agency that deals with discrimination claims.
Keeping track of what is going on as it is going on is the best documentation–each day or once a week write down any actions/comments that you believe were inappropriate, and include how it made you feel/how it is affecting you (you’re nervous, irritable, feel like you want to quit, hate coming to work, get nausea, etc.) If another co-worker witnesses anything, ask them if they would be willing to write down what they saw. This may be tricky if you are the supervisor, so make sure they know you are not ordering them to do anything. If they won’t write anything, or if you are uncomfortable asking them, write down the incident in as much detail as you can–this way, if months pass before they are asked about it, the details may help them remember the incident.
Finally, make sure you protect yourself from a counterclaim–don’t tease or flirt with any employees, and discourage it among all the employees you supervise. Granted, in most workplaces a bit of flirting may be taken as good fun, but you can’t be seen as engaging in or allowing any type of behavior that you find inappropriate in her, so this may mean being hyper-sensitive until this is resolved. As much as possible, deal with this woman only when another supervisor or co-worker is around. Keep all conversations with her work-related, at least as much as possible without becoming openly hostile towards her (saying hello, goodbye, etc. but don’t talk about what you did over the weekend).
Hostile workplace harassment is all about respect, and women can be just as disrespectful as men. Good luck with this and feel free to e-mail me if you think I can be of any help (email address is in my profile)