Hi jokeru, how are you?
I'm not from Zaragoza, but maybe I can help you with some things.
There are some good places to go on Zaragoza, like Puerto Venecia (if your girlfriend like shopping, she'll love this place, and maybe your wallet won't), Plaza del Pilar and Basílica del Pilar (you will found it in the same Plaza del Pilar, of course).
Zaragoza have lots of places to have some drinks and dance (just if you want
) at night. Believe me, a lot of places.
In Zaragoza the temperature is very low and cold, especially in Delicias (also know as "the world cold factory"...), so please bring some good wearing. It's not summer anymore there :S
You can go to Barcelona and Madrid by Ave (I think it's the best way). Check all the information you need here
(https://www.trenes.com/ave/?gclid=CLrD6IrotckCFSkXwwodqlMF...), and of course, if you need something to be translated, notice me.
I'm pretty sure someone from Zaragoza (or not) will answer you in a more good way than I just did.
I hope you have a really nice vacation with your girlfriend and like our country.
Cheers,
Gerard.