You Can't Bluff the Sharp-Eyed Sister 1

In the sleepy countryside of Mythos, young Chloe trains as a priestess by day and secretly wins big money at cards by night. Her success captures the attention of Erald, a paladin of renowned looks and wealth, and he is convinced she has a magical gift that may be key to solving a murder from two years prior. While Chloe insists on being ordinary, the promise of riches beyond her imagination has her racing headlong into a tangled web of political intrigue…

Volume 1 of the You Can't Bluff the Sharp-Eyed Sister manga series by Yo Asami.