You need to explain to her very carefully in a mellow, patient, and sympathetic voice. It's the only way to get through people like this.
Trust me, I have to deal with my mom and technology all the time.
Also, she doesn't know how to use the Internet so she de-activated it and now I'm tethering it from my phone in the middle of no-where, therefore I only get Edge at about 15 KB/s.
Can't even watch a loving YouTube video.
EDIT: Explain to her that if you don't save manually, such as your sister didn't, it won't be saved. She simply forgot to save and it was a simple mistake on her part.