You mean "my friend", right? If you do, you say mon copain or ma copine.
To say "be my girlfriend" in French, you can say "sois ma copine."
ma copine
Tu es ma copine
"C'est ma petite copine."
j'aime ma petite amie, j'aime ma copine
yes if the friend is a girl!
Ma petite amie. or in slang in some regions - ma Blonde. Mon amie, or Ma copine
"Quoi de neuf ma copine?" is a French expression that translates to "What's new, my friend?" or "What's up, my friend?" It is a casual way of asking someone what is happening in their life or if there are any new developments or updates to share.
You can say "Ma petite amie m'a largué."
copine
Une copine may be either a female buddy or a girlfriend. This is to be deduced from context.