Anywho know a few good Idioms?

I have a friend who likes to... "give advice" before she knows the full story of whats going on. I do appreciate the advice she tries to give but it in a way its very irritating when she isn't aware of the full story. I've been nice and keep my mouth shut when she does it but after constantly doing it for so long it's starting to get bothersome. She's the type of person who can't be bluntly told to not give her honest opinion and advice until she fully knows what going on. With her I have to word things carefully so she doesn't get so offended she completely flies off the deep end so to say. I've found using Idioms is the best way to tell her to knock her **** off. Does anyone know a good Idiom pertaining to don't give advice until you know the full story. A good example would be "Don't say the Defendant is guilty until you've heard his plea/case."