Children's book from 80-90's

Hello,

I am searching for the title of a book I had read as a child way back in 1986.
It tells the story of a very kind old widow who is adored by the children of the neighborhood. When her husband dies, she is left with no financial means, but apparently, her husband left treasures hidden in their house for her to find and use. When her money runs out, the children help her search the house, till they find a great hidden treasure.
I think the book cover was blue, with a drawing of Ms. ??? And the children, by I do not remember clearly. I will appreciate any suggestion.

Sea View Secret by Elizabeth Kinsey (ie. Eleanor Clymer)?

One of the Mrs. Piggle Wiggle books has this.

Mrs. Piggle-Wiggle series. https://www.librarything.com/nseries/3254/Mrs-Piggle-Wiggle

Thank you so much! I believe this is it. Do you know which one of the books it would be in?

I think it's in Mrs. Piggle-Wiggle's Magic