I agree that it's likely she was using Facebook, and at any rate she should've been driving more carefully. Her excuse is that the sun was blinding her- I say if the sun is blinding you then you need to slow the fuck down so you can stop quickly. The point I want to make is that you keep talking about evidence but there's not really any of that around yet. She apparently lives about 2 miles from where the accident happened, so it's entirely possible that she send the post from her driveway before she left, put her phone in a safe place, and then drove like a maniac for 2 miles and accidentally killed some guy (who shouldn't've been talking on his cell phone in the road, but I digress...). Just because the Facebook post time matches the time that the guy was on the phone doesn't prove that she was using Facebook at the time because of the objections I raise in my last post.
This is a screwed up situation. The guy should have been standing somewhere safe while he was chatting with 911 about the fender bender. The girl may have been using Facebook on her phone, but the bottom line is she wasn't being careful enough if she hit a guy in a populated area because she couldn't see well due to sun glare. If you can't see, slow the fuck down until you can see far enough ahead that you can stop if there's something in your path. However, unless we can see packet headers with an originating IP from her phone and a destination IP to one of Facebook's IPs within a few seconds of her hitting the guy, there's no real evidence.