How does she know that her customers actually paid her? Without something that is connected to the network she has zero way of knowing with any kind of certainty that she actually will get paid.
Doesn't she have a phone (didn't watch the whole video)? Even if not she could ask her customers to show her the tx details on their phones (right after payment is made).
Don't really see a problem here. There's always some risk of double-spend attempt if she doesn't wait for confirmation, but I don't think anyone would try that for such small value service.
There's probably much higher risk of someone simply refusing to pay and walking/running away.