Myrna got a notification that she needed to run special software in order to get back on Facebook. Leo says that chances are good that Myrna downloaded a virus. She has to be careful when responding to popups. They're usually "phishing" scams designed to get her to run a scan or download software. It's a red flag that they're going to break into her system and use it. Since Myrna fell for it, the only safe thing to do is back up her data, format the hard drive, and reinstall Windows from a known, good source.
She should also check out this page on Facebook.com.