Found: Only remember the cover but need title to find...

...it was about a girl who was talking to an old lady ghost that would materialize in a chair. In the attic I think. The cover has a drawing of the old woman in the chair. She has a black long sleeved dress on,looks sad,and her hair is in a huge white bun. The girl has on a plaid shirt or dress and has spiky black hair and is looking at the ghost with eyelids lowered. I read it back in the 70s so it must have been published before then.

Miss Ghost by Ruth M. Arthur?

OMG that's it!! Thank you so much!!