Again, following the line of thinking that valonqar is a gender-neutral term, then one of the major candidates has to be Daenerys Targaryen, who also very much fits the bill for the younger, more beautiful Queen as well. Dany has her eyes on the Iron Throne and ruling Westeros, and if she's to get there then she'll have to overthrow the current power, i.e. the Lannisters. That would include Cersei, although - like with Margaery - it's a bit more difficult to imagine her literally wrapping her hands around her throat and choking the life out of her. For Daenerys and a number of others, it's necessary to think that may not be literal (although you never know what people are capable of). Of course, there's a sticking point to all of this: it necessitates Dany actually getting a move on and heading to Westeros. Guess this one ain't happening then...