Should I tell my girlfriend that her breath smells weird?
Why do you think her breath smelled weird?
It smells like something spoiled or rotten.
This could be a delicate subject to bring up. Find a way to mention it so that she's not offended. Maybe offer her some gum or a mint?
She ate tuna salad and that's what did it. She shouldn't eat things that make her breath smell like that.
It's good to be honest with others but too much honesty can be hurtful. Make sure you don't hurt her feelings and just try to tolerate her breath as well as you can. We all have days where our breath is not as fresh as it could be.