Enabling my Mother in Law to stay in Ireland

My Mother in Law has arrived from Peru on a Visitor's visa. My wife likes the idea of her staying with us indefinitely. I dont have any issues with that (no Mother in Law jokes please) as she is very nice.
I understand that she can possibly apply for a Stamp 4 as a member of my wife's household. Would that be possible on a visitor's visa that states "no extensions"?
As I cannot get a job in my profession I am window cleaning atm. My wife is house cleaning for about 12 hours a week. We are getting a weekly top-up from the government. Would this count against us?
Any thoughts?
Thank you.