All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
First of all, we alert our Muslim brothers and sisters that it is impermissible to go to soothsayers and diviners, even if the intention is simply to ask them, let alone believing what they say, as has previously been shown in Fataawa 82923 and 85109. Besides, there are ways prescribed by Allaah The Almighty to remove the effect of magic, which we have previously clarified in Fatwa 88660.
A Muslim, in principle, is innocent, and it is impermissible to accuse him/her of doing magic on somebody without clear evidence; and the statement of that soothsayer is not reliable evidence in this issue. For this reason, it is impermissible to publicize that accusation, and whoever does so is sinful. It is also impermissible to listen to that, for it is to listen to falsehood, and whoever listens to it is also sinful.
On the other hand, it was your duty to advise your mother in a good manner, on the basis that it is impermissible to mention that speech, or, at least, to excuse yourself politely from listening to the details. Moreover, that your mother mentioned to you the details in the course of her answer to your question about the state of the sick person does not make it permissible for you to continue to listen to this falsehood after your mother went on relating the details. So, you must repent of that sin.
Allaah Knows best.