Currents / Jane Petrik Smolik.

Enhanced descriptions from Syndetics:

This middle-grade historical novel follows three young girls living very different lives who are connected by one bottle that makes two journeys across the ocean. It's 1854 and eleven-year-old Bones is a slave on a Virginia plantation. When she finds her name in the slave-record book, she rips it out, rolls it up, and sets it free, corked inside a bottle alongside the carved peach pit heart her long-lost father made for her. Across the Atlantic on the Isle of Wight, motherless Lady Bess Kent and her sister discover Bones's bottle half-buried on the beach. Leaving Bones's name where it began and keeping the peach pit heart for herself, Bess hides her mother's pearl-encrusted cross necklace in the bottles so her scheming stepmother, Elsie, can't sell it off like she's done with other family heirlooms. When Harry, a local stonemason's son, takes the fall for Elsie's thefts, Bess works with her seafaring friend, Chap, to help him escape. She gives the bottle to Harry and tells him to sell the cross. Back across the Atlantic in Boston, Mary Margaret Casey and her father are at the docks when Mary Margaret spies something shiny. Her father fishes it out of the water, and they use the cross to pay for a much needed doctor's visit for Mary Margaret's ailing sister. As Bess did, Mary Margaret leaves Bones's name where it belongs. An epilogue returns briefly to each girl, completing the circle of the three unexpectedly interconnected lives.