Found: YA novel girl runs away to live w/sister

Read this in 2012. A young girl leaves home (dad and step mom) to live with her older sister in their hometown. Their mom died a long time ago. Older sister told her that many years ago, a part of their town was swallowed by water, now the ghosts live underwater. Sister seems to have magic powers and eventually younger sister realizes she is using a force field of sorts to block out contacts from the outside world (everything outside of their hometown). Younger sister wasn’t able to get calls or hear from anyone outside of their town. Older sister also uses these powers to control the people around her and keep the younger sister from leaving. She eventually is able to leave and the older sister joins the ghosts underwater I believe???

Imaginary Girls by Nova Ren Suma?

YES OMG THANK YOUUUU!!! I have been looking for this book for years!