Can she take my truck away from me?

I bought a truck with my girlfriend about a year ago. Her credit was much better than mine, so we purchased it with her as the primary to get a lower interest rate. I have had possession of the truck since the purchase, and all of the payments are made via direct withdraw from my bank account. She is now trying to take the truck away from me by threatening to refinance it under her name only. Can she do this? - Is this your question? Add additional information