Reference: Fataawa Noor ‘alad-Darb – Question No.6110, Pages 524-525, Volume 11
Question: If my mother is required to make an expiation, is it permissible for me to do so on her behalf?
Response: Yes, if anyone is required to make an expiation – and someone else then makes the expiation on their behalf, then there is no harm in that. That is because [in doing so] he is like her representative. So if her representative was to pay off the expiation, or [even] make a charitable donation, then his representation [on her behalf] is valid and correct; and this is [the case] whether or not he spent from his mother’s wealth or his own.