The protagonist cares for her grandmother, who is not well.
The only part of this that really registered on Amy was “union pay and
full medical benefits.” My God, that could mean hospital care for
Gran, a safe apartment, enough to eat . . . Much more fiercely than
she intended, she turned on the woman. “Would I be able to put my
grandmother on my medical care? I’m her sole support.”
The woman blinked. “You’re guardian for your grandmother? At sixteen?”
“Not legally. But she’s ill and I take care of her.”
She wants money for medicine for her grandmother:
Money for whatever medicine Gran might need, a new TV instead of an
old pawned one, new jeans—
She isn't quite her sister's guardian:
Gran was Kaylie’s guardian and had been Amy’s until she turned
Given that her grandmother is ill, though, she does take care of her.
She is selected for a reality TV show:
“I’m Alex Everett,” the bald man said. “Before we do the rest of the
introductions, let me explain for those of you who still don’t
understand what you’re doing here.” He winked at Amy, who kept her
face as blank as she could manage. “You lucky seven have been chosen
from hundreds of applicants for Taunton Life Network’s newest show,
Who Knows People, Baby—You? Myra Townsend and I are the producers, and
this is how the show works.”
I couldn't find anything about endorsing toys or books, but the rest is an exact match.