my fiancee and i are looking at buying a car together before we are married. whose policy should it be on?

Contact another insurance agent.  Your insurance agent should be able to tell if your state allows for automatic coverage of passengers in your vehicle, including co-owners.  title is not the issue, it is how you are insured. In other words, if your parents insure their car, but include you as an authorized driver, you are both covered.  Try your state's insurance dept for help.

Your fiancee could get a new policy with just her name on it.  Then the question becomes, do you currently live together?  If so, everyone in your household must be listed on your insurance policy as an additional insured if they have a license.  On the other hand, if you live separately, you could use her car with her permission and be covered.  Then, after you are married you can combine policies. 

Unless there is a quirk in Wyoming law of which I am unaware, this should solve the problem.  Run this by your insurance agent and see what they say.