I stayed in Teresa's studio for 3 nights while visiting Porto. Teresa always answered promptly to my messages, gave me lots of information and tips about the city and the check in went smoothly (even if I arrived almost at midnight).
The studio was comfortable, with twin beds, wardrobe, flat tv (which I didn't use), bathroom and kitchenette. Teresa also left a small treat on the table for my arrival.
The position is perfect to visit Porto, being 20 minutes walk from Ribeira, 10-15 minutes from the Station Sao Bento; around the flat you can find tasty local restaurants, cafes and a minimarket. The studio can be a bit loud if you keep the window open since it faces a big street; I had absolutely no problem sleeping thanks to earplugs.
I would definitely stay again.