On some AA planes, the first class seats are leather. Very slippery. The aisle and center arm rest are large and fixed. A cushion for her back will aid her in finding a more comfortable position. Also a foot rest or small suitcase under her feet will help to avoid the fatigure of trying not to slip on the leather seats. If she is over 5' 6" or so this may not be a problem.

Her own (clean) travel blanket may be a help also.

Good luck!