So my GF who I've been with for over a year now told me there's a new guy at her school who is passionate about art and tattoos...something she is incredibly passionate about. She told me that she should probably ask him to teach her and stuff.
At first, I was going to tell her how that made me nervous but than I just pretended like I didn't care... And I guess she caught on and new I was I guess kind of irritated.
I am an artist in my own way but this new guy is more into the art my GF is into...
How should I react to situations like these?
Should I bring it up to her or simply just focus on myself?
Is she testing me?
She is going to be in the same school as this guy for the next year or so and I'm going to be somewhere else. Should I be worried?

Find a girl with the same interests as you and do the same to her. Girls are replaceable. Get out of the scarcity mindset.

First question is: Do you trust her?

If the answer is no, you shouldn't be with her.

If the answer is yes, then let her do what she likes.

I think it's a good sign that she's told you about it instead of doing it behind your back. Shows respect... and I also think it's probably less likely she's going to cheat on you if you know where she is, what she's doing, etc.

Ask to meet the dude, if you are concerned about it.