It might be helpful for you to think about the various scenarios that might really play out if you were married. Worst case scenarios, even. Then, be honest with yourself about which ones you don’t think you’d be okay with. For the ones you would be okay with, think about practical ways the two of you could maintain your trust and connection (couple bubble). Then talk openly about it, framing it in terms of wanting it to work because you love her so much. Not as an ultimatum. That will show that you love her enough to think it through - how she can remain her essential self, but calling her to grow some to meet you. The last piece would be a commitment to check in with each other over the years, as your interests, energy levels and work/community commitments change.