I would not get the one from western powders, it comes with an o-ring to put under the primer. I think I remember hearing they wear out after about 16 shots.
Here is the CVA BH 209 breech plug for about $5.00 less than you can buy it at CVA.
http://www.lg-outdoors.com/proddetail.asp?prod=80873 you don't need a rubber o-ring.
I would start your daughter out at 80 grains of BH 209 powder and increase it by 5 grains, until she says she is comfortable with the shot. Good Luck and Good Shooting.
I checked one more place since the other was out of stock
https://www.midsouthshooterssupply.c...r_Loose_Powder This one is out of stock also. gives you 2 places to check back with.
CVA.Com is also out of the BH 209 Breech plug. Between one of the three I would think you would find one in stock soon, its a hot item.
I have been using the CVA breech plug for 2 years and never had an issue.
Note: Use a 1/8" drill bit to clean the flash channel every 3 to 6 shots, The flash channel is the channel under the primer. Put black tape around the shank of the bit until you can grip it firmly. Use finger pressure only.