treacle, what kind of hamster do you have and why is she weak? does it differ with the different species? i have a syrian and he is 7 weeks old, yet he spends most of the night running in his wheel which makes me wonder why yours isnt strong enough? also, mine chews at the bars too - not frequently but sometimes. but yesterday when i took him out of his cage for the first time since buying him, he didnt chew on hte bars at all and just went on his wheel which makes me think maybe your hammy is a bit bored and has loads of energy to burn? try to take her out of the cage, see if it makes a difference? put those wooden chewy things in her cage too, see if it helps