Thunderstorms can be scary for dogs with anxiety | Patricia McConnell | McConnell Publishing Inc.
Above is some information regarding counter conditioning your dog to help with fear of thunder
And some threads below. I'm sure someone will come along with some more ideas. Good luck with your girl.
Scared of thunder Thunder Training is Helping!
Dexter Bartolomeo -GSD (24 months)
Fluffy Cornelius - Maltipoo rescue (approx 7yrs)
Squeezette Antoinette- Shih Tzu (16 yrs)