Too much lipstick looks trashy. I dab really lightly on my bottom lip with a pinkish redish color and then put on clear gloss and rub onto my top lip. It helps my lips to look fuller but natural. Start out with a flesh color and then graduate to a deeper color.
I don't wear lipstick. I hate makeup. And it tastes disgusting when you lick your lips. Tell your gf that if she doesn't like your lips, then you'll go kiss someone else's.