I believe you can remove a folder from the sidebar by right clicking the mouse and deleting it.
I use the column view and used to enlarge the width of the column next to a list of pictures to get a bigger preview. One little trick I just learned in the column view is to right click on the mouse on a picture and go down to "Quick Look." Then if you just use the up and down arrows, you can preview your pics continuously at a large size.
When she saves something, she should click on the arrow to the right of the save window so she can see the sidebar and put things in their proper place and not just save to the default place. One other thing I do is set the browser to "ask me" when downloading a file where to put it instead of everything ending up in the downloads file. I'm also not sure if she understands that folders spring open when you hold things over them rather than just drop them in, so she can drag a file to a folder, wait for that folder to open and then decide where to put something.
I don't know if anyone but me still uses paper folders with papers filed in them, but if she gets that, she should be able to understand the Hierarchical File System.
