UPDATE:
There was an intervention by the university today. They sat down with Stephanie and told her everything that she had done, and made it explicitly clear that it is NOT my issue but hers and that she needs to knock it the fuck off. They set parameters on her such that she is not allowed to email me or send me text messages and, since we still live together, to keep communication to an absolute minimum. They told me that if she steps anywhere out of these bounds I should not hesitate to call them and, if necessary, the police.
This is a great relief, since when the university people called me they told me they made things brutally clear to her, so I now feel comfortable being in my house, and if anything shitty continues, she'll likely be thrown the fuck out.
So basically, whether she stays on good behavior or bad, I am able to carry on with my life with peace of mind.
So at this point the conflict may be at a resolution. We now return to our regularly scheduled forum banter.