Not you mother,
sister, female cousin or female friend. A female that once you’ve officially established is your exclusive partner (i.e., intimate, peer,
best friend), you want to kiss without her asking you. More importantly, when she asks for a kiss you give it up without question. And, even more notably, you are able to kiss without the expectation that you will get laid.
In conclusion, a girlfriend is a female that (particularly in the initial stages of the
relationship) you want to make feel special and wanted (not rejected/unwanted) by showing her affection through the simple act of a passionate kiss.
Female:
Baby, give me a kiss before you
go.
Male: Leans over and kisses the girlfriend passionately then leaves (all without going for grabs or wanting to get lucky).