If a sister wants the inheritance to go to her sister equally, it is better for her if she finds another way to void the will because just giving it to her sister is a taxable gift, So, the estate gets taxed, then the gift itself is again taxed (to the giver) and if enough, to the recipient. So, some other way, if done legally, so that the normal recipients (two daughters) would share the actual estate equally.
Just in the interests of taxes etc. (No, I'm not an accountant or lawyer, I have been involved in an estate in which a disinherited child figured into the picture-along with a wife who was illegally/unethically divorced, a live in GF who had helped the man in his last months(a verbal promise had been made) and 9 other kids(who had been gifted or not with parts of the estate at the last minute and whose claims were ?'d by court) and an ex wife that he tried to remarry right before his death so that she would get his SS benefits-yeah, it was a doozy). It was only $100,000 and really not worth the hassle.