Marella was wonderful. Met us at our arranged time, spent lots of time explaining the city and giving us her personal suggestions (which were fabulous), and made us feel at home. She even had a bottle of wine waiting for us :)
As for the apartment, you couldn't ask for a better location! Be prepared for it to be warm in summer, as there is no AC, but we found the space to be delightful and more than enough for all our needs. Great bathroom, nice little kitchen, beautiful decor; we loved it.
Our highest recommendation. We will stay here again if we are in Florence!