Also if you're using low powered ammo you could try hotter ammo, it should bounce forward off the brass deflector. My low powered stuff angles off around 4 o'clock while stronger stuff goes out around 2-3.
I am a lefty. There is a brass deflector that just clips on the upper right by the ejection port. I was issued one when I was in the army. My AR doesnt put brass in my face. So I havent bothered to look for one. It is a small piece. Unless you know what it is you would not know one if you saw it. I will see if I can find a pic somewhere. Cant be too expensive. I would be suprised if is was more than $20 or $30. Unless you are purchasing for the military then it is probably $600. LOL.
There are two companies that make a good left handed model. Stag and Rock River's New Lefty. Both are excellent weapons. The new Rock River is 100% left handed with the ejection port door even flipping down like the right handed version rifles. The other suggestion is to get her into another position on the rifle. She may be crowding the ejection port and if so even the deflector may not deflect the cartridge away from her with out hitting her. That is an unpleasant situation since they can even put little brand marks on your cheek. Like the older M-16 A-1 use to put a little circle brand mark on the left handed shooters cheek. So if using this rifle "position on the stock and rifle are the key. If she was shooting prone open the stock up more (Extended) which should help if it is a collapsible stock for example.
Good Luck! Just do not want to let it discourage her from shooting weapons! Not worth ruining a good thing!