We all know Dany only did it to make her name longer
Daenerys Stormborn of House Targaryen, the First of Her Name, Queen of the Andals and the First Men, Protector of the Seven Kingdoms, the Mother of Dragons, the Khaleesi of the Great Grass Sea, the Unburnt, the Breaker of Chains and the Mad Queen of Ashes.
But she might have to strike "Protector of the Seven Kingdoms" from her name.
T'was but a single city of a mere 1 million peasants. What is one City in comparison to protecting the rest of the Seven Kingdoms from the White Walkers?