[esw]

I sincerely hope that this post is an awful joke, because the way in which you're talking about your girlfriend is appalling. If this isn't a troll, then it sounds to me like your girlfriend agreed to be a part of your project because she loves you, not because she has some burning desire to [do whatever your startup does]. If that's the case, then no management technique is going to inspire her - she's doing it for you, not for the startup.

[andrew_gardener]

To further this point, it might not be the end of your relationship if you encourage her to seek meaningful employment in whatever expertise she has from her PHD. It doesn't sound like she's as interested as you think she is in your start-up.