You can find other patients here at Marrwoforums, ellmp, and also through the free
Peer Support Network service of the Aplastic Anemia & MDS International Foundation (AA&MDSIF). Call 800-747-2820 and ask them to find others you can talk to, who have faced a similar situation. You, your mother, and even your father can take advantage of it.
My wife had ATG and cyclosporine and I remember when she couldn't stay up for more than a few minutes at a time. A low red cell count can leave you weak and exhausted, give you headaches, and turn even little tasks into big challenges, so it's easy to get discouraged. After her ATG my wife got gradually stronger and was able to do more and more. I hope your mother does the same. Having a bad reaction to horse ATG and then an infection were certainly setbacks, but perhaps this time the ATG will kick in. It's a treatment with a very good track record.
It's important to get treatment from doctors who are experienced with aplastic anemia. Is your mother being treated at the Cancer Institute of New Jersey? They have that kind of expertise.
Since well-matched platelets give your mother a better and presumably longer benefit, I suggest asking if the blood bank is making the appropriate efforts to find her good matches. Some centers are able to identify particular donors who are good matches for particular patients.
I hope you are able to be there to support your father for at least some of the long hours he's spending in the hospital with your mother. It's hard to maintain your optimism when things haven't gone well, so I hope that hearing from others who have traveled this road will help you and your parents regain a positive outlook.