Answer: Do it anyway -- by yourself! There's no doubt that Unification can do wonders for people who practice Unification with each other. But if either party, having been introduced to the idea, is not naturally enthusiastic about it, you can still do wonders for the relationship by practicing Unification independently.
Needless to say, no one should ever be pressured into performing Unification practice. No one can practice Unification effectively unless they sincerely WANT to do it.