"Where does your Spanish girlfriend live?"
Translation:¿Dónde vive tu novia española?
"... Just asking since I'm going to Spain this weekend and wouldn't like her to feel ... Alone.." - who came up with this sentence? How many girlfriends do you have? One in each country?
It said I was wrong because I used the tu form vives, which I did because I used tu!!! Why is that not correct?
"Tú" and "tu" are different - with the accent it means you; without, it means your.
Here, the actual subject of the sentence is "novia", so we need to use "vive". Hope that helps!
The word, española, is an adjective. Many spanish adjectives must match the gender of the noun they modify.
In addition to your first mistake, the interrogative adverb, dónde, requires an accent in this Spanish sentence.