Poor little one, I almost cried last year I was so frustrated and scared of fulldowns.
Things that helped me:
- ride the pop by taking a big breath - so her bases count 1 2 3 (down) 4 (up) 5 (BREATHE IN) and then tuck your head into the left collarbone (not too hard, she doesn't want to bruise her chin or her collarbone). Taking the breath should help her ride the pop, engage her core and hold her hips and shoulders square.
- dish shape, she wants to hit that hollow position so practice rocking back at forth holding the dish shape and also visualise hitting this in the full, you almost want to fold your body in half vertically so you keep everything in tight - toes together, arms together, I even pull my shoulders in together when I'm doubling.
- close your eyes, if I spot the ground I'll stop twisting, so I squeeze everything tight until I'm caught and stop spinning, open my eyes, and hope to see my pretty bases smiling down at me. Probably makes for terrible facials, but at least I get round!
And just keep hugging her and tell her not to panic. Easier said than done, but I hope she gets it soon. Maybe practicing with her bases outside normal training might help, even just a few minutes before or after, so the pressure is off. Good luck!