Good effort, but unfortunately your wide open aperture didn't do you any favors. Be very careful taking close-ups at 1.8 because focus is tricky and depth of field (DOF) is EXTREMELY shallow. In the first photo, you missed the focus on the eyes completely. In the last two photos, because of the shallow DOF and the turned head, your niece's right eye is in focus but her left eye (and just about everything else in the photo) is blurry. If you were to try again, either stop down the aperture to at least 2.8 or stand farther from your subject to shoot at 1.8 and crop the photo for the close-up look.
I had the same experience when I first shot with my 50 mm at 1.8 and I remember it well... I shot what should've been a gorgeous photo of my two year old daughter. Unfortunately for me, the focus on the tip of her nose was razor sharp but her eyes were blurry.