Do you have full knobs on her bike? Put a dedicated sand tire on the front, it makes all the difference, especially while learning sand.
On the West side of 314A (SE 160 Ave), North of 464C and South of SR 40 is good riding for a n00b. Not too much sand out there, but it will be wet right now. Some of the mud holes are easy to cross, some not so much.
You won't do much riding in ONF without sand, I would just take her straight to the powerline and have her ride standing up in 2nd gear until she gets it.
Here is a tired woman, after riding the powerline.
Sand, its whats for dinner.
This is in the area I was talking about.