standard are about 4-5 weeks old, so they should be dying especially if fresh to her shop. i would suggest if the room they were kept in gets to -2 then you should find somewhere warmed to keep them, so they are not getting too cold,really anything under 16c can start to kill crickets, -2 is like putting them in a fridge,
think about what it feels like if you come in doors when its -2 outside then put your hands on a radiator, it hurts, so this same thing stresses the crickets and can cause them to die.
i also reconmend buying some bug grub or fish food or crush up some dog food in a coffee grinder
i work for a insect farm so i no quite abit about live food product, i probably work for you girlsfriends supplier