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.

Although the tip feature/QR code on her bike does make sense for when she would receive payments that she doesn't need to know for sure will eventually get confirmed (and as a result few/no people will attempt to fake and ten double spend a tx to that address), she still needs to know that she will be paid when her customers actually pay their fairs