It's perfectly understandable that you don't want to put either of your children through the transplant process, if it can be avoided. Your daughter's doctor has probably told you that it can take many months to see if her bone marrow function is restored by the ATG/cyclosporine/prednisone treatment. Tapering these drugs must be done very slowly, so the extent of her recovery may not be known for quite a while. Then you will be faced with the uncertainty about whether the improvements are permanent. Her SAA could eventually return.
The flipside is that a transplant, while unpleasant, can cure SAA. The good news is that ATG and matched sibling transplants both have excellent track records for youngsters so the odds are in your daughter's favor.
By the way, cyclosporine is probably the cause of her high blood pressure, assuming she had no previous medical issues.
To help you make this difficult decision, I suggest getting a second opinion at a treatment center that has expertise with SAA, such as the
Helen Diller Family Comprehensive Cancer Center at UCSF or the
Stanford Medical Center.