I'm going to tell my girlfriend there are more important things in my life than her
That sounds pretty harsh, what makes you want to say it to your girlfriend?
Believe me, I cherish my time with her.
If you cherish your time with her, you would not be saying this. It will upset her to hear such a thing.
The truth is I'm toying with her emotions and making her upset.
It is wrong to do that to your girlfriend. Imagine that she did this to you, how would you feel? I can't imagine you would like it, so don't do it to her.