Instead of adding additional text to the presentation itself, I showed her how to add notes in the "Presenter's Notes" section. This area allows you to use most of the basic formatting features and therefore is great for taking notes. The best part is that when this file is now opened up in the Google Drive app for mobile devices, you can activate the "Presenter's Notes" and the screen of your device will be split between the original teacher notes and your supplementary notes.
I have provided a video tutorial of how to do this below. There are some variations to some of the steps, but I thought this would be a good basic introduction to the concept. Let me know what you think.