I am not sure if the % is less if you do it earlier. But say she works till 60 that will give her 41 years.
41 years * 2 % = 82% of her top pay
I believe they contribute 8% a month to retirement, so she will no longer be doing that, but she will essentially be getting 90% of what she was making but not have to go to work. Teachers do no pay into social security, so she won't have anything else coming in, but a 10% pay cut and not have to work at all, ever again, sounds pretty good to me.