[Eternal]

Everyone is different when it comes to sexual activity. Some people display pleasure more prominently than others. So just because she appears to be more turned on than you, doesn't mean that it's true. Besides, being more turned on can't be compared to how much feelings you have for someone. People with lower sex drives are still able to fall in love.
If you really love your girlfriend and believe you love her just as much as she loves you, then there isn't a problem. Try to just enjoy your relationship rather than worry about who loves who more. The only important thing is if you both have feelings for each other.