"What management strategies would you use to reach this person, get them more invested, and help bring out their passion?" Consider for a moment that your star

"What management strategies would you use to reach this person, get them more invested, and help bring out their passion?" Consider for a moment that your startup (or any startup) is genuinely not her passion. Otherwise, she would have been working at a startup already. This situation is obviously a strain on your relationship & I would strongly advise that you stop trying to force it continuing. Be honest with each other, perhaps this isn't what is best for her career, for your business and for your relationship with each other.