I actually don't mind her head being so far back because she is trying to show her neck. The problem is with the eyes, they need to be either soft or strong. but she is not doing either
For me, the huge issue here is the mouth, though her whole posture is just so inelegant. And now I suddenly had a mental image of this being one side of a tampon advert (you know, they always have one showing the clearly uncomfortable looking woman, presumably using a cheaper brand that apparently sends shocks up her lady parts based on how much they exaggerate it)