They may charge the $50 SDC fee if she is not a GM or higher, assuming there are seats on the later flight. If she is running late and thinks she is going to miss it, then I'd recommend calling before missing the flight. If it ends up full or oversold, then she could be stuck there.

If she misconnects because of WX or MX they'll reroute or put her on the next available flight. Unlikely to be rerouted on another carrier unless MX and she has status, and there are no other options.