If your fiance has put the car in their name, and the other automobile policy and registration is in your name, it is most likely that the insurance policies will have to remain separate, until you marry. You can check with your insurance company(ies) to see if they have a better idea, but for the time being you are two separate "entities". If you have the same insurance company they may handle it differently.
Your fiance's insurance company will want you listed as a driver on their policy, but if you have any tickets or accidents they should not charge you, since you have your own separate insurance policy. Make sure the insurance company is aware of the separate insurance.
Your fiance could put your name on the registration and then you could combine the insurance to one policy, presuming that is what you want to do. It will give a multi car discount to that policy if you don't already have that.
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