Sonia's place is in an absolutely perfect location. The river is steps away, as are some great restaurants. Makes for fantastic romantic walks at night. Porto is very walkable in general and we never needed to use the train to get from her place to wherever we needed to go in the city.
It's also adorable and colorful, and fairly large for a 1 bedroom apartment (admittedly I live somewhere with notoriously small apartments.) It gets so much natural light as well due to the large windowed doors to the small patio spaces and a skylight in the kitchen.
Sonia gave us a bunch of tips on arrival while going over a map of Porto, and she left a great bottle of wine for us to enjoy as well!!!
I'd absolutely stay there again on a return visit to Porto.