Your girl friend may contact her employer whether they have another copy of the H1 prroval notice (I-797A, not I-797C). If her employer have the I-797A and that should have the I-94 with it, she does not need to go to US Canada border to get the I-94. She need to ask the employer to give the original I-797A to her for her travel and provide that I-94 to the Airlines when she leaves for China.