I'm going to tell my gf that her breathe stinks
Are you trying to be insulting?
I just think it's disgusting that it stinks.
I understand that you find it disgusting that your gf's breath stinks but you should find a polite way to tell her. Maybe offer her gum or mints.
She must say thank you and then kiss me while I pull her deep into the kiss.
If you tell her so bluntly that she has bad breath I doubt her first thought would be to kiss you.  You are more likely to get slapped if you can't come up with a nicer way to say it.