I'm thinking of flirting with other girls even though I'm in love with my girlfriend
Are you kidding? What girls are you flirting with?
Some acquaintances, maybe ask them for their phone number or such?
You are with your girlfriend you shouldn't be doing things like that. You need to be respectful and not look at other people.
I'll choose the most beautiful one and flirt with them a bit
That's a terribly mean thing to do to your girlfriend. You should only have eyes for her and that's it.