SOLVED. YA book, main character Cathy, staying with grandma. [s]

[Kylen]

The book is from the early 1980s, probably about 150 to 200 pages. The main character, Cathy, is staying with her grandmother during the summer on an island. Cathy makes friends with a woman artist, who also owns a cat. Cathy is working through some stuff, and she's been told her mother died when she was a young child (she's about 12 to 13 here). There is also an older guy with a boat and a dog named MacDuff. Cathy like peanut butter ice cream, too, if that's a detail that rings a bell.

Spoilers: the woman artist whom Cathy befriends turns out to be her mother. Her father divorced her and cut off all contact with her because she was an alcoholic who was emotionally abusive to him and Cathy. She eventually finds out the secret, and her father allows her to reconnect with her mother, who is now in AA.

[Ayshe]

Now Is Not Too Late maybe?

[Kylen]

That's right, Ayshe! Thank you so much!