I agree you were right to separate them, it sounds like they were really not getting along.
Next time you get a pair you know to research more and make sure you do all you can to reduce the risk of trouble but it won't hurt them to live alone now
Chewy will adjust to life on her own in time and its better shes alone than badly injured.
Keeping same-sex pairs is actually pretty unnatural with hamsters
In the wild any pairs or groups would always contain both genders. I feel its always worth giving hams a chance to live in same sex pairs or groups but its never the end of the world for them if it doesn't work out