We didn't actually meet Amy during our visit to San Sebastian which is a bit of a pity as I have never met a Kiwi that wasn't anything other than soooo friendly and helpful. Amy always responded exceedingly quickly to any emails or questions that I had.
You will have a great stay in Amy's flat. The location is perfectly suited for the old town and close to many great bars and of course the famous pintxos. The spacious flat has everything that you need although (in my opinion) if you are spending a lot of time in the flat then you're doing something seriously wrong. San Sebastian has so much to offer the visitor that you can't help but fall in love with this wonderful city. It's easy walking to both of the 2 main beaches.
Other visitors have mentioned the noise. This is only an issue in the front bedroom, and was only Friday & Saturday night. My wife slept, but I struggled as it was loud and continued late. I've stayed in many Spanish cities before, so I'm not completely naive, but earplugs might help. But did it spoil my enjoyment? No. Would I go again? Absolutely!!!