Muslims cannot inherit from Christians

Dear REspected Mufti
I have read on ask imaam.com that Muslims cannot inherit from Christians however if the christiaan parents bequeth not more than one third of the estate whils they are alive then thi scan be accepted. MY wifes father has told her that when he dies she will get a property as he will leave one for each of his kids. Does this equate to a wasiya and can this then be accepted by my wife? Shukran