Doppelganger Jumper by Judy Lyn Gregg

"Let me be the adult and you concentrate on being a child."

"Thanks for the thought, Aunt Nora, but I'm too old and worn down to be a child who revels in fairy tales, little pets, and imaginative adventures."

Sixteen-year-old Abigail Azure's mother is in a coma, dying. Her abusive father is on the run, and Abigail is plucked from her life and transported to the home of her Aunt Nora. Her aunt, allegedly a wailing banshee, claims Abigail has a jumping gift buried deep within her that allows her to visit other realms populated by doppelgängers from her home world. This banshee and jumping stuff feels like nonsense to Abigail until she jumps, travels to another realm, and maybe falls in love. She can't get distracted now because her mother is running out of time, and medical technology is proving inept.

Abigail resolves to use her gift to gain control of her fate and help her mother. But her dad shows up, and he has a plan of his own.