Answer: Social anxiety
Step-by-step explanation:
Social anxiety disorder is defined as the disorder in which a person tends fear from being judged negatively or being rejected for particular social situation.this social phobia causes extreme anxiety and distress to the person and thus, they avoid social gathering-like situation .
According to the question,Penny might be suffering from social anxiety disorder as she keeps rejecting dinner invitation, speaking in public events etc.She might feel anxious due to fear of being negatively evaluated in social gathering by friends and other people .