RE: What size shafts for 40# recurve?
Offhand- 1816's. You don't give her draw length, but I'd guesstimate around 24" You can fine tune arrowflight by changing point weight. You might have to use 5/16" points- they look a bit funny on a 9/32" shaft, but they work fine. 1716's might be a better choice in the short run, but the 1816's will grow with her.
BTW- skinny shafts can be a pain to fletch helically- I use a straight offset feather, unless I plan on mounting broadheads.