Request #238

There’s a book and I can’t remember the title or author.  It was YA from the 80’s and it had a really long title, something like Part Time Beginner Experimental High School Witch.  The main character and her sister move with their parents to Florida where the main character finds a diary with witch spells in it in the attic.  She starts trying to perform the spells in her spare time as she slowly gets to know people and make friends.  Her sister does ballet and has lessons.  She falls right before an audition and gets hurt.  The sister misses the audition and the main character thinks she was responsible.  The main character starts thinking she’s responsible for bad things that happen around her until she meets the person who wrote the diary in the first place, and she realizes something, and I forget everything that happens.  The cover seemed to be fantasy but the book itself was more of a realistic coming of age novel, if I remember right.  Help?  Thanks!