DarkHeartsMarching,
It is very doubtful that bone cancer would affect both thighs. Also, it is the normal circadium rhythm for our body temperatures to go up as much as two degree F during the night. It keeps our bodies warm during down time at night.
She is right in the age for growing pains. Yes, they are real. The following is from the KidsHealth website, you can read the whole article by googling "KidsHealth Growing Pains":
"Your 8-year-old son wakes up crying in the night complaining that his legs are throbbing. You rub them and soothe him as much as you can, but you're uncertain about whether to give him any medication or take him to the doctor.
Sound familiar? Your child is probably experiencing growing pains, a normal occurrence in about 25% to 40% of children. They generally strike during two periods: in early childhood among 3- to 5-year-olds and, later, in 8- to 12-year-olds.
What Causes Them?
No firm evidence shows that the growth of bones causes pain. The most likely causes are the aches and discomforts resulting from the jumping, climbing, and running that active kids do during the day. The pains can occur after a child has had a particularly athletic day.
Signs and Symptoms
Growing pains always concentrate in the muscles, rather than the joints. Most kids report pains in the front of their thighs, in the calves, or behind the knees. Whereas joints affected by more serious diseases are swollen, red, tender, or warm, the joints of kids experiencing growing pains appear normal.
Although growing pains often strike in late afternoon or early evening before bed, pain can sometimes wake a sleeping child. The intensity of the pain varies from child to child, and most kids don't experience the pains every day..."
There is much more on the website about Diagnosis, Treatment, etc.
If however, the pains becomes persistent enough to keep her from doing her usual activities, then she may need to see someone. Good luck.