How did he change the title to her house without her consent ? While I do not practice law in your state, normally that can only be done by a notarized deed from the owner. If he forged her name, in the states were I practice, he would not have legal title.
I think your cousin's mother should speak with an attorney as soon as possible to file a lawsuit to set aside the property transfer and to file a notice in the deed records that ownership of the property is in dispute. At this point if she is there without a deed in her name or on a lease, he can file an eviction notice. He must first give her 60 days advance written notice that he is requiring her to leave the property.