Hmmmm…..I’m sure you’ll get some marvelous suggestions, but I’ll start the list with Betsy Tacy by Maud Hart Lovelace. And then, depending on how she likes that one, she could read the next one to three books in the series.
Other books I’d recommend, depending on how much she likes to read, are Charlotte’s Web by EB White and Thimble Summer by Elizabeth Enright. These two and Rascal by Sterling North are probably my favorite three “summer” books. If you look at them and think she wouldn’t like to or be able to read them fluently, they would be perfect read-alouds.