Daughter of Smoke & Bone by Laini Taylor. It was published in 2011, and is the first book in the Daughter of Smoke & Bone trilogy.
The main character is a teenager named Karou, who lives a double life as an art student in Prague, and an errand girl for an "inhuman creature" named Brimstone, who runs a shop in another dimension.
In general, Karou managed to keep her two lives in balance. On the one hand, she was a seventeen-year-old art student in Prague; on the other, errand girl to an inhuman creature who was the closest thing she had to family.
Even though she had lived in Brimstone's shop, she still didn't understand where it was, only that you could enter through doorways all over the world and end up right here. As a child she used to ask Brimstone where exactly "here" was, only to be told "Elsewhere."
Brimstone was not a fan of questions.
Karou wears a beaded necklace, and can use each individual bead to make a small wish, referred to as a "scuppy".
It was a very small wish. These beads were just scuppies, after all. Like money, wishes came in denominations, and scuppies were mere pennies. Weaker even than pennies, because unlike coins, wishes couldn't be compounded. Pennies you could add up to dollars, but scuppies were only ever just scuppies, and whole strands of them, like this necklace, would never add up to a more potent wish, just plenty of very small, nearly useless wishes.
She used a more potent wish, referred to as a shing, to turn her hair blue:
Brimstone wasn't stingy with scuppies. He let her refresh her necklace as often as she liked from his chipped teacups full of beads, and he paid her bronze shings for the errands she ran for him. A shing was the next denomination of wish, and it could do more than a scuppy -- Svetlar's caterpillar eyebrows were a case in point, as were Karou's tatoo removal and her blue hair -- but she had never gotten her hands on a wish that could work any real magic.
And she speaks more than twenty languages:
Unearthly, the wail rose, wavering and violent, to break like a wave and become language -- susurrous, without hard consonants. The modulations suggested words, but the language was alien even to Karou, who had more than twenty in her collection.
You can read a preview of the book here.