We loved staying at Joana's apartment! The location is amazing and the space was perfect for the two of us. We didn't actually meet Joana, but her father greeted us and was very accommodating. Porto was absolutely amazing and such an amazing city - wish we could have stayed longer!
Make sure to research exactly where the apartment is - we had trouble finding it as it's on a very small street. Even some locals couldn't help us! Once we found it we were thrilled with the location, but just be prepared. Also, the hot water doesn't last that long in the shower - it wasn't a problem for us, but just plan accordingly - it's only enough for one longer shower... so we just two quick showers each day.
Overall it was a perfect place for us - we loved it! Highly recommended.