A children's book from 50's-70's about a girl who moved to a house with a staircase in a turret with velvet curtains where she liked to read... also another from the same time, one about a girl who lived near an abandoned house where she used to go and play and fixed it up and maybe ended up living there? I remember both books (vaguely!) from childhood and would love to read them with my daughter...

The first is vaguely familiar, but I'd need more details.

As for the second, try Mandy, by Julie Edwards (Julie Andrews). It might be what you're looking for.

It's a young adult book from the 1980's. The main character was a very talented artist, but is severely abused by her alcoholic mother. A boy tries to reach out to her, but she has to keep their friendship a secret?

First one sounds like "The Velvet Room."