i dont think the valanqar is part of the prophesy in the show. she didnt say those words. thats a book thingI loved the finale! But the show is adhering to Queen C's prophecy so far and a younger brother must kill her.
The only way she can quickly gain an alliance is through marriage so I think that and her ruthlessness snaps Jaime's crazy loose and she gets it. Or The Imp finds a handy stool to stand on while she's prone on the floor in a wine haze & strangles her. Him little starfish hands are adorbs
arya is gonna take out cersei in the finale season 7 imo. maybe AS jamie's face. but thats just an easter egg to the valanqar prohesy from the books (which will be different)