u/Feisty_Succotash8917

In the late 70s, early 80s, I swear I read a book about a young girl visiting her Aunt, who is always starting a new hobby. The aunt is a little scattered, and this time she has taken up witchcraft. The Aunt leaves for her exam and doesn't wait for her familiar, so the young girl and the familiar chase after her. The Aunt got messages in cupcakes that she had to wear special glasses to read? And there was a doll house that they had to shrink to enter? I can't find anything about this book anywhere, anyone else remember it?