Barbara would like to update to macOS High Sierra, but she thinks that she can't update it because she hasn't updated in a long time. Leo says you can. The way you can do it is to go to the last version your computer can handle directly. If that's macOS High Sierra, then just go to the app store download it and install. If you're getting notifications, then you're golden. It'll take awhile though.
Does she really need to backup? Leo says that back-up are important to preserve your data, and Time Machine will do that, but only locally. To be REALLY safe, you want to have off site backup as well. That way, if your house burns down, you still have your data. For pictures, Google Photos will give you unlimited hi resolution photo backup. Flickr gives you 1TB of photo storage. Apple's iCloud gives you 5GB. Amazon Prime members get unlimited photo backup.
Just remember, one backup isn't really a backup at all. What you want is 3 copies. 2 forms of media. 1 off site.