Thank you for your question
My name is Clare
I shall do my best to help you but I need some further information first
Do you mean within a Will?
Has your mother told you why she is doing this?
But has she told you why she has chosen to do this?
Have you asked her?
It is possible in Northern Ireland to do this I am afraid.
However you can if necessary challenge the Will if you believe that your sister has exercised Undue Influence.
You can read more about challenging a Will here
Please ask if you need further details