I'm an 8b and things winter sow just fine here. The seeds don't need to freeze, temps averaging around 40F, or about the same temp as most refrigerators are more than adequate to provide the chill. Warmer days, colder nights than approximately 40F with the temps fluctuating back and forth work out quite well. Tell her to have fun sowing....

Liatris spicata though will often germinate with no chill at temps of 65-68. If she hasn't done much seed sowing she may find winter sowing easiest but its not required.