The application demo in your presentation is not meant to be a systematic overview of features. Instead, you want to give the investor/customer the most powerful impression of what the app can do. Dragging her through menus, sign-in pages, and settings gives a realistic impression of what it is like to work with your app, but it is a boring 5 minutes inside your 20 minute pitch.
Describe a problem , show what you would enter into a search box , show what a beautiful solution your apps produces instantly. Three screen shots instead of 15 pages of live demo which are better left for the next meeting.