Maria was an amazing host! Although we didn't get the chance to meet her, we could tell she really cared for her guests and her home. The place is run like a hotel and is clean, orderly, and spacious. Her home is secluded from the busy street with a lovely front garden and porch. It was an easy 20 minute walk into the centre of the city (you'll need it after all the Pastéis de Nata you'll be eating!).
Our only downfall was that some other guests tended not to respect the space (i.e. we were provided with a bath mat to keep the floor dry, but some guests just wet the whole bathroom floor which was slippery) but that's really a hit or miss. Otherwise, I would 100% recommend anyone staying in Porto to stay at Maria's place!