Hi Serellyn,
The code sample you are looking at looks fine. Basically, your menus are created and managed by the Gameinstance. The gameinstance creates at game launch and ends on shut down. There is only ever 1 gameinstance and in that content example there should be a derived gameinstance blueprint.
The behavior you see is expected to be IsValid, because there was never a command to destroy nor was any parent of the widget garbage collected.
What actually happens? Do you get a black screen? Try adding the “-log” to the standalone command line to spit out more data.