Last I heard, you said you had found the problem, not sure if you can implement it or not.
For those wondering I had tried to make a 'Save Heather' mod some time back - not by telling her to stay outside, but actually fighting against the Sabbat in Hallowbrook basement to keep her alive.
I had pretty much balanced it out: it's the most difficult encounter in the game by far - Heather is vulnerable to friendly fire, so you have to be careful with guns, and if you don't get to her soon enough, she's toast. But it IS possible.
I always thought Wesp's "stay in the birdcage in the sky" was sort of the pussy way out.
She's MY ghoul dammit! NOBODY lays hands on her but me!!!