Sounds like she has a problem.. are you going to get that fixed or just sell her onto someone else and give them that problem?
Rearing is VERY dangerous. But there may be a reason she rears. Maybe the BO was too rough with her, maybe her teeth need to be floated, maybe the saddle hurts, maybe she isn't sound.
Figure it out, get it fixed, and then find her a home if you aren't comfortable.
"Strength is the ability to use a muscle without tension"