I would highly recommend staying at Maria's place. The location was perfect — it was centrally located and near the metro, which made getting around on foot or by metro very easy.
The space was as advertised and perfect for our needs. We spent many evenings eating dinner or drinking cava out on her balcony porch, and the sunset view from there is not to be missed. Bonus: If you go for New Year's, you can see the fireworks from Placa España from there! Maria also stocked the kitchen with some snacks to get us started, and provided many essentials for cooking, such as spices, and coffee.
Maria is a fantastic host who really went out of her way to make us feel welcome and help us with all our questions. She met us at the house and gave us a ton of recommendations for restaurants and grocery stores, and was available via WhatsApp throughout the trip to answer any questions and provide additional recommendations about events she'd heard about we might be interested in. She was a great resource and definitely added to the quality of our trip!
Thanks for hosting us and making our trip to Barcelona so wonderful!