It's nice when you share common interests, but it's also a good thing to have your own.
I've dated girls with no real interest in MMA, but they were happy to watch a card with me every now and then and I did my best to inform them and make it more entertaining for them when it happened. In return I'd do stuff they wanted to do, and the cycle continued.
Never be afraid to go outside your comfort zone either.
Is it a big deal for you and the girl you are dating/your girlfriend to share common interests? Or you could give a shit about trivial stuff like that?