That looks like an urgent (i.e. today) vet appointment is needed to me. You probably need to call an emergency vet to get an appointment booked ASAP.
As a side note, if she is female, do you know if she was kept in a tank with any males in the pet shop? Did they tell you Snowey was male/ kept with males?
When you get to a vet, get them to double check Snowey's sex, as female hamsters can be prone to certain reproductive issues (although this would be less common in the younger hamster).
Does Snowey still seem healthy otherwise? Be prepared to set up an emergency bin cage in case the vet wants you to put Snowey in a hospital cage. Do you have enough funds for vet treatment (you should be able to claim this back from the pet shop, so keep all receipts)?
I don't think this illness would have been caused by food, although I'm not a vet.
Edit: If you can, please update the title of this thread to say Snowey is unwell.
