Tell her ...you have the same problem and uou get very ashamed of it and as to how you are plannig to get rid of it. Maybe she doesn't even know she had it.

I would buy her toothbrush for her birthday

We were kinda dating and I was planning on kissing her one night but after discovering the bad breath I slowly stopped my relationship with her.

Negerata

I was about to kiss her just a little before I said the weather is not good today and turned away not to see her again.