It should be D! Overjoyed!
Gloria is beyond happy, it even states in the passage that she couldn't stop smiling after her performance.
So basically let's break down the rest of these responses -
A.) Reassured! She doesn't need reassurance - she seems to know she'd done flawlessly during the play.
B.) Frustrated! She's happy so that's not right.
C.) Shocked! That doesn't quite fit either - no where does it state that she even hesitated let alone is shocked!
I hope all is well, and you pass! Good luck, rockstar! You deserve it! (:
