My sister is saying she will run away to avoid going to jail should I tell someone?

my 21 year old sister has to go to jail for four months for a hit and run while driving under influence. She has to go next week. She told me she is going to run away so she doesn't have to go because she is scared and nervous of going. This seems silly to me because I don't know where she will go but it looks like she might be serious and the panic she is showing is definitely genuine. What can I say to talk her out of it, also should I tell my parents? What will they probably do? Some say call the police or ask my parents to call, but I am not sure if I can do that. I am close to her and don't want to betray her you know. If I tell them what could they do? Is there anything I can say myself to help stop her or convince her not to do this and to just properly report?