Ideas to include
What you want her to know
The one thing you would want her to hear on her worst day. Say it flatly in the brief, and the song will carry it.
Her, not a daughter
Her actual stubbornness, her actual laugh, the thing she does that nobody else does. Specific beats sweet, every time.
The women she comes from
A grandmother's name, a family line, the traits that skipped a generation and landed on her anyway.