Aya is a young girl working at a brothel in Braavos.
It isn't clear if she is actually a child prostitute or just a servant girl working at the brothel, though, considering her common attire and state of general confusion when presented to Trant, the latter is likely.
The Braavosi madam is present when Ser Meryn Trant visits the brothel she works in, seeking a prostitute. She presents three prostitutes - an unnamed prostitute, Brea, and Anara - to him, but he claims that they are all too old. Realizing with some distaste what Trant is seeking, she presents him with a very young serving girl. Trant informs the madam that he expects a "fresh" one tomorrow night, again to her distaste. Throughout the exchange, the Madam is vexed by the presence of "Lanna", a young oyster-seller, so deep in the brothel, and warns her not to show up there again.
|Game of Thrones: Season 5 appearances|
|The Wars to Come||The House of Black and White||High Sparrow||Sons of the Harpy||Kill the Boy|
|Unbowed, Unbent, Unbroken||The Gift||Hardhome||The Dance of Dragons||Mother's Mercy|
In the books
In the A Song of Ice and Fire novels, there is no such character.