If that was my problem, I'd google: reactive attachment disorder to learn what I could about that disorder and then I'd leave the kid alone to nurture her self and go to sleep when she is ready to.
I used to baby sit a little girl in our neighborhood and when it was her bedtime, I took her to her bed, laid down beside her and read aloud from a children's book. Within minutes she was SOUND ASLEEP!
I became their favorite baby sitter!
For a child having a "fit", I would calmly and patiently stay near the kid and allow the feelings and actions to gradually dissipate on their own so long as nothing dangerous or harmful is happening.
good luck,
jim