Can you countersue in a probate case?

My aunt had past away and did a quit claim deed to her sister a year before she died. They were very close. Now there is a daughter that came out of the woodworks and claims that the property belongs to her. My aunt was divorced with possibly two children and one cannot be found. Daughter claims she is the only one. My aunt who always mention she never wanted to leave her kids anything because of their drug abuse. My aunt and her daughter never had a relationship. Now the daughter is claiming that her mother had dementia for several years so she didn't know what she was signing. No where ever was there a doctor that diagnosed my aunt with dementia. She also claims that fraud was involved and other accusations. Close family members and friends of my aunt can testify to this. My aunt lived alone and did for herself. Can we countersue this daughter for attorney fees and slander, emotional distress for what this deceased sister is going through?