Well, it's good see a topic using the show to know what may happen in the books. I have wished to do this sinse the Shirren's sacrifice, but I didn't know where to write. So, thank you.
I don't see this happening, no with the clues Martin gave us. And some characters don't get to to what they do on show. Cersei is pretty donkey and Euron is pretty dangerous. We know that a character from the show is a mix of several characters from the books and the events, as well. So, what may happen in the books?
In the first place, I reckon we will have more than 2 books. It's much story to tell in just 2 ones. In second, I believe that the youger and prettier queen is not Dany. If she was, Cersei survived to Euron and Cersei is not capable. And Dany still needs to solve her problems in Slave's Bay and to find ships to go to Westeros. It may took some time.
No, IMO, ththe younger and prettier queen is Lynesse Hightower, the queen of the love and beauty. In book 4, one of the Hightower's siblings was to Lys to ask help to her to win Euron. What happens: she helps, 'couse this is the time to come back to Westeros. But when she finds Euron, they become lovers. She is the woman in the Aerion's vision. She is the woman that Cersei needs to know, as well. What d'you think what will happen when Euron conquer KL? I see sacks, rapes and sacrifices in the septum and Cersei losing the Iron Throne. But I also see the other queen, a Hightower that has lived in Lys using Qyburn to make experiences with Cersei, turn the Lannister in another Reek, taking away from Cersei her beauty and Lannister proud, making Cersei to beg the Gods to send the valonqar to kill her.
So, when Dany comes she will find Stannis with Davos, Melisandre, and the support of the North, Vale and Trident, thanks Sansa. Aegon will have Varys and the support of Stornslands, Dorne and part of the Reach. And Euron and Lynesse will Iron's Slands, Westlands and the other part of the Reach. Oh, and Dragonstone. Dany will have a huge army and a huge fleet as well. And 3 dragons. Her council will have Marwin as Maester, Tyrion as Hand, her own husband Victarion in charge of the Iron Fleet.
But her army has people from different cultures and this may a problem for Dany. She needs harmony between her allies. Tyrion will be bitter and he be playing with Dany and Aegon. It was this I understood Moqorro saw in his flames. And Vicatarion is donkey.
Dany have huge army and fleet, but all are foreigns or cruel. And Dany is with the prophecies about betrayals in his mind and the notice of Qarthe to not to trust in the griff, the dark flame, the lion, etc.
So, she may have an allegiance with Aegon, but she will never believe him or whoever. And to show she is the only Targaryen, she will make Aegon attacks KL first. So, when Aegon is midst the fight, Dany attacks the army and fleet of Aegon and Lynesse at the same time.