So, after spending a week in Maria's flat, I can tell you it is absolutely amazing!
The apartment is very spacious, clean, and it was decorated with style and simplicity. The interior court is SO cool as well. The place is very quiet and the interior court is filled with plants which is soothing to the eye. Once you get acquainted with the city, you can easily get to the historical center by walking for about 5 minutes.
Maria and Angela were very responsive and helpful in terms of getting around, the must-see sites, and all the cool tapas bars and restaurants. Spot on!
I highly recommend Maria's place for an absolutely lovely stay in Seville!