LMo- sounds like she gave you a taste of what obsession feels like by putting her thoughts to you so you can empathize. Sometimes the only communication we have when we feel "crazy" is to drive someone else crazy too.
if you must do something how about notify the webmaster of the danger to others she might pose- then let them handle cleaning their own house-
then I'd shore up your boundaries maybe for your own comfort cause she got way too cozy in your head it seems- so put her out like you would anything thats not housebroken and leaning on you for nourishment.
FBI has online reporting of online weirdos that you can make a complaint - in VA but its not anonymous- you have to tell who you are. So give it to the sites webmaster imho and step away from the plate.