Roflstompette

A debbie downer; a girl or woman who ruins the fun for others by pointing out that funny comments, jokes, or situations are in some way inappropriate and therefore should not be laughed at.

See roflstomper.

Me: funny comment

Debbie: insufferable remark about inappropriateness of funny comment

everyone: awkward non-laugh at funny comment, mixed with eyerolls at Debbie

Conclusion: Debbie is a roflstompette.