Well you don't call someone a girl friend, they're your girlfriend or your friend. I was considered correct in my translation "This friend has a cat".
What I would like to know is - in this situation, is it considered to be your girlfriend or your friend? Diese meaning "this" I'm presuming friend since it would be odd to say "this girlfriend" without meaning that the person has had a lot of girlfriends.
You are right! "Eine Freundin" is a female friend. If I was talking about my girlfriend I would say "Meine Freundin" (it's the same in Dutch). As far as I know the English language doesn't have separate words for female and male friend, so "This friend has a cat" is the only right translation.
Not a native speaker, but I believe it is as follows:
Meine Freundin = my girlfriend
Eine Freundin von mir = my female friend (a friend of mine)
Mein Freund = my boyfriend
Ein Freund von mir = my male friend
I'm also given to understand that a woman may say "meine Freundin" to mean a female friend (and not necessarily lesbian girlfriend), much like in English a woman can say "I'm going out to see a movie with my girlfriend" and mean her female friend, but a guy would never say "I'm going out to shoot pool with my boyfriend" because it either doesn't work that way or we're so afraid of our sexuality that we don't use it. (I'm pretty comfortable with my sexuality, but I don't think I'd use boyfriend. Maybe it is a language thing?)
From the intro it says: "That means, "der," "die" and "das" can also mean "that (one)" or "this (one)" depending on the gender of the respective noun, and "die" can mean "these" or "those.""
So does that mean we can use Die to mean "this" when used as a pronoun but have to use Diese to mean "this" as a descriptor?
ie: "This friend has a cat" Diese Freundin hat eine Katze
"This is a cat" Die ist eine Katze
Which intro are you referring to?
You can use the definite articles (der, das, die) as demonstrative pronouns - this (one) or that (one) - without the noun. When saying this is, that is, these are or those are, it is more common to just use das, regardless of the gender:
Das ist eine Katze = This is a cat or That is a cat
Dieser (and dieses, dies, diese) is typically used to emphasise the thing you are referring to. You can use dieser either as a determiner before a noun, or as a demonstrative pronoun in place of the noun:
Diese Katze ist schwarz = This cat is black
Diese ist schwarz = This (one) is black
Again, it is common to use dies regardless of gender when saying this is or these are:
Dies ist eine Katze = This is a cat
Dies sind Katzen = These are cats
Is it common in Germany to ask a new acquaintance "Does your friend have a cat?" I imagine the appropriate response must be to start pointing around the room (or photo album or Facebook) and saying things like "This friend has a cat, that friend has no cat, the other friend has seven cats and will presumably die an old maid."
"This girlfriend has a cat" wasn't accepted. I got one wrong earlier in the lesson for saying 'this friend' for 'diese Freundin'. I'm really confused as to why the same thing, sans context, is being treated totally differently. What was there to distinguish that this one was not "Girlfriend" but the other was?