I have an urgent dilemma: my sister's moving out of state, but she hasn't told my parents about it. She tells me they're against the idea, and given my experience talking to them in the past, I believe her. She seems determined to leave regardless of the circumstances (most of her stuff is already at the apartment she's moving into) , and she's set up an entire plan to leave without them noticing. It involves me to a high degree, however. I have to take her to the airport, come back home and pretend she left on her own after dropping off at work.
I'm wondering how I should handle this situation: should I tell my parents she's moving out of state, should I play ignorant, or should I do something else entirely?