Is copine masculine or feminine

copine means both girlfriend, or a friend who is a girl. This is a casual term used by both girls and guys. You have to deduce the meaning from the context. Also, when talking about a girlfriend, a French speaker is likely to add a singular possessive : ma / ta / sa (= my / your / his)

qui est cette fille ? (who's that girl?) - c'est sa copine = his girlfriend;

qui est cette fille ? - c'est une copine à lui, c'est une de ses copines (a friend of his, one of his friends)