Four out of five [souls] ain't bad...

As a die-hard Hellraiser fan and someone who can appreciate all the films (even the later ones), I've found one major loophole in this film that I can't explain no matter how many times I watch it. Maybe someone can find the logic in this...

Kirsty promises Pinhead five souls in exchange for saving her own (and all of this before the accident, of course). Four of them make perfect sense. Trevor cheated on her with his boss and lusted after the neighbor; Kirsty probably had some inkling of this when she made the pact. His shady co-worker's suicide made enough sense, and Trevor's own death requires no explanation. What doesn't make sense to me is Sage's murder. Trevor didn't start seeing her until pain from the "accident" required him to do so--by which time he's actually dead. So Trevor never cheated on Kirsty with her in the real world, and there is no evidence that she existed anywhere outside of Trevor's own personal hell. So how could she logically be one of Kirsty's five chosen victims?

I think I'm typing myself in circles here, but an insightful theory would be much appreciated (and no, that doesn't mean negative commentary like, "Because the movie sucks and there is not plot...").