No, I don't necessarily think you should eat the fees, and certainly not all of them.
There is no doubt Peggy owes $34.
The other $34 is between you and Susan. Most likely Susan feels like an idiot and will assume responsibility for it.
But: She can also make a reasonable argument that she is not responsible for the default since she would have made it on time (assuming she feels that she would have), and thus been able to play doubles as scheduled, had you not intervened. Under this logic, since the unneccessary intervention was yours, the financial consequences are yours too.
Moreover, she can try to argue that it was her call to make and not yours (although I no longer think this is a valid argument based on your description of the dynamic between you and your teammates).