Tagging your luggage all the way through your final destination isn't the same as not having to re-checkking your lugagge at a first point of entry. Flying CZ, DL...doesn't make a difference. Guess your GF learned that the hard way.

It could be worse...you could be flying Delta or any US airline to the US.

Going through security...Answering same old questions during boarding Delta flight...
Waiting...answering same old questions during point of entry US.
Reclaim/recheck baggage and going through security again.
Boarding next Delta flight....


That takes even longer.