Contest my mother’s will

To challenge the will the burden is on you to show lack of capacity.  You will need health records.  It is a very expensive proceeding.  You also have the burden on undue influence, and this is also hard to show. 

There are several issues involved here- your grandparents' wills, the nature of their bequest to your mother, your aunt's possible undue influence over your mother, and whose name is on the deed to the house. These questions can only be answered by reviewing the relevant documents- the wills, the deed, and your mother's medical records, to determine if she was unduly.influenced to change her will to exclude you. If she was, depending upon whether the estate is in the middle of probate or letters have already been issued, the appropriate application can be made to Surrogate's Court to enforce your rights, if they've been violated.