Upvote:3
Yes, she needs a C-1 visa to change planes in the US, because the US has no exit border controls, so domestic and international flights aren't segregated in the departures area. In addition, it is possible to exit the departures area without any checks.
Thus, anyone touching down at a US airport must enter the US.
This fact is stated in Timatic, the database used by Airlines.
There are no TWOV facilities available in the USA
(TWOV=transit without visa)