A relative is flying domestic DL, connecting to an international flight on VS. It's a VS ticket, Y on the domestic portion and C on the international. She has two checked bags, is a silver on VS.

On arrival (tiny airport, not DL staff) she's been charged 100 for the second bag. They claim because the first flight is domestic Y, only one checked bag allowed.

I believe that is incorrect, due to the segment in C and her being a STE.

Have the check in staff got it wrong?