I am sorry to say that you are probably not going to succeed with the argument that you were coerced into signing that agreement. It was not signed under duress as far as I can tell (like a Magistrate or Judge will tell you, no one held a gun to your head) and it was not induced by fraud. It can be argued successfully by both your mother and the bank that it was or should reasonably have been contemplated by you that there might be a possibility that she could not keep up with the payments. More to the point, the bank did not 'coerce' you into signing the agreement.
So, sadly, ABSA is under no obligation to do anything about this. It is between you and your mother.
There is a couple of options that you have:
1. Either you and your mother can agree to sell the place.
2. If she does not agree to sell the place, then you can actually approach the court and obtain a judgment that would force her to sell the place or that would force her to sell her share to you, where after you can sell the place.
3. You can agree with your mother to sell her half to you and then rent the place to her.
So, unfortunately, the bank would be totally within their rights to hold either or both of you liable for the payment. Until such time that the issues can be resolved, if your mother is in arrears, the only way to prevent your credit record from being affected badly would be to cover the payments yourself.
I sincerely ***** ***** I am making sense here, but if you have follow up questions before you rate, feel free to ask them at no extra cost. If you are satisfied with the service, kindly rate it positively.