I'm going to cause a scene to get the heat off my sister
What kind of heat are you referring to?
The heat over her illicit affair
I'm sorry your sister was involved in an affair. It may be better if you let her deal with the consequences instead of trying to distract from the situation.
What makes you think that the news of the affair is a bad thing?
It's never good to cheat on your partner. Your sister should deal with the consequences of her actions.