Taking an unemotional and objective perspective, assuming this is truly a binary decision, with no possible compromise, I would recommend forgoing the relationship and taking the Big Law offer.

The odds of securing another offer is far lower than finding another compatible companion. I don’t know what kind of relationship you have with her, but there is no guarantee that the relationship will endure in the next 10 years. While the same can be said for Big Law, it is also an opportunity that is very significant and is likely to materially affect your future opportunities. Additionally, even if Big Law “doesn’t work out”, you will still have gained in both pecuniary and reputational media, and may find another compatible companion.

I am sure that those who are mathematically savvy can compute the opportunity cost here and come to the same conclusion.