We had a lovely stay at Silvia's house. It is indeed in the center of Venice, and you can reach Piazza St.Marco very easily by foot.
We stayed in a private bedroom with our own bathroom which was good.
The cats are friendly so no worries about that.
Our host, Silvia's mom, was very friendly and spoke English, Italian, French, was you wish :)
The house is really big and very pitoresc.
Will come back for sure!!