The Highlander method doesn't work ???

Prove that his immortality hasn't gotten passed onto her by killing her in a logic field.

I'm joining up soon, and my specialty will be Yu Yu Hakusho. I suppose I could loan you a Sinning Tree or a Pseudocreature.

I like the idea of doing 1 and then 2. Acting like the Mafia is always fun, even if I did confuse them with raffia once.
-Mad Maudlin

Why not try taking care of her Highlander style, with a quick decapitation?

Here's an idea - release some sort of massive Biblical demon that feeds on life energy, and, when they've killed each other, CUT HER LIPS OFF. That way no bloody Welsh police officers can snog her and bring her back.

Stick her in a sun and turn up the TARDIS's internal time vs external time. (ala "the Runaway Bride" formation of the Earth). The Sue should end up spending her life energy rather quickly. That, or hook her up to New New York's power grid.

Having the Sue's immortality disappear in a puff of logic is such a nice thing, don't you agree?

It wasn't just a black hole. What the man said was "the event horizon of a collapsing galaxy". Which is about ten orders of magnitude larger. Like Pads says, those are very good shields.

You might want to consider how Upstairs will take leaving a 'Sue alive, even if she's trapped, though. They got rather ticked off at Jay and Acacia for leaving one to the Elves, as I recall.

hS

A pity I'm too recent to join... I don't have permission yet, so I won't be able to help you with my (future) team of agents with a TARDIS

I like the last one too. Although now that I think about it, the TARDIS must have incredible shields to actually be able to drop someone in a black hole...