I like much of this, you have a nice dramatic look and she appears very lovely.
I agree that the pose is off. Her shoulder looks enormous (although, interestingly, as a graphical element it balances her face well) and her expression is ambiguous, nervous?
You did well on the technical stuff, but the soft skills of posing and making her feel at ease, feel sexy and beautiful, it seems like these need work. That's the harder stuff, though, so don't feel bad! Ultimately, she does look sexy and beautiful here, but she could look a lot more so.