Summer of the Gypsy Moths pdf by Sara Pennypacker
Stella loves living with Great-aunt Louise in her big old house near the water on Cape Cod for many reasons, but mostly because Louise likes routine as much as she does, something Stella appreciates since her mom is, well, kind of unreliable. So while Mom "finds herself," Stella fantasizes that someday she'll come back to the Cape and settle down. The only obstacle to her plan? Angel, the foster kid Louise has taken in. Angel couldn't be less like her name—she's tough and prickly, and the girls hardly speak to each other.
But when tragedy unexpectedly strikes, Stella and Angel are forced to rely on each other to survive, and they learn that they are stronger together than they could have imagined. And over the course of the summer they discover the one thing they do have in common: dreams of finally belonging to a real family.