What am I doing wrong?

I have two chinchillas that I have looked after for the same amount of time and both are treated equally. Their behaviour is completely opposite and for some reason one of them kind of hates me and the other doesn’t. She won’t come out of the cage and if she does it’s because I’ve had to try and pick her up - which she really doesn’t like and tries to run off as fast as possible, but if I don’t I worry that she won’t be getting any exercise. Sometimes I just let her stay in the cage because...

What am I doing wrong?