The word Freundin can mean either a girlfriend or a female friend. In some cases, they can be distinguished by using the possessive pronoun to refer to the former:
Ich habe mit meiner Freundin (girlfriend) gegessen.
Ich habe mit einer Freundin (female friend) gegessen.
Sometimes, though, this isn't possible. For example, how to translate these sentences?
-- How was your trip?
-- Great, I've met a new (girl)friend.
A drink for my (girl)friend too, please.
How is this distinction usually made?