Can I change the date of my High-speed train ticket between Beijing – Shanghai?

My girlfriend was planning on coming from Shanghai to Beijing using the High-speed rail on the Friday and returning on the Sunday. I therefore booked her the return (Beij - Shang) using her ID card number at a ticket office in Beijing - as she had her passport in Shanghai. However she missed her outbound trip and is now coming on Monday. Will it be possible for me to change the date of her Beijing - Shanghai return trip without any form of ID (as she still has this in Shanghai and will not arrive until after the ticketed departure date). I already asked to be refunded and was refused without her passport.