If Jarla was smart - she would divorce Mike now and leave with guaranteed HALF.
If she waits for Mike to die, she is bound to the will.
If he dies and leaves the money to the children and her, she will only get 1/4.
Hell, he could leave all the money to the children and nothing to her.
If she wants the money, she should divorce him now and leave with her 1/2 and she can start spending it before she becomes a bitter old lady who is pissed she wasted her youth with an old man.