This looks like it may be the A Witch's Brew set, which consists of the following six books:
- The Thing at the Foot of the Bed by Maria Leach
- The Secret of the Sachem's Tree by E.N. Monjo
- Miss Clafooty and the Demon by J. David Townsend ~ Illustrated by Edward Gorey
- The Strange Story of the Frog Who Became a Prince by Elinor Lander Horwitz
- Timothy and Two Witches by Margaret Storey
- The Witch's Egg by Madeleine Edmondson
Found with a search for timothy "two witches" "sachem"
Based on your description of an imp bothering an old lady, I suspect you're looking for Miss Clafooty and the Demon by J. David Townsend.
Violet Clafooty was a miser! She lived in undisturbed serenity in the kitchen of a house so large no one knew how many rooms there were, and hoarded a stockingful of coins. She refused to spend a single coin, even for clothing. Miss Clafooty would walk down the street in her old-fashioned, patched, and pinned hand-me-downs and floppy picture hat. If people stared, boys hooted, and dogs snapped, she hardly noticed. Then visitors threatened Miss Clafooty's way of life; and the final visitor - the demon - was the most threatening of all.
Black and white illustrations by Edward Gorey successfully capture the spirit of this amusing tale about a miser who outwits all of her guests but one! A story boys and girls are sure to enjoy.