Cat is not trusting of certain person?

We've had the cat for about 4 months now. Although she was very scared at first, I'd say she trusts me completely (I can pick her up, she sleeps on my back next to me, etc.) but it doesn't work with my mother. She does run around her legs but is much more cautious with her and gets scared more quickly. If my mother, for example, moves her hand too quickly towards her, she jumps away. My mother has never done anything that could have scared the cat. It was clear that she could have trusted me more because whenever she first ventured out from under the cupboard, I spent a lot of time with her and approached her very slowly, but I don't understand why she's so scared of my mother. The only reason why this could be the case is that the cat was previously caught by a cat catcher and examined by a vet, and is therefore generally more cautious around women. Unfortunately, I sometimes notice that my mother is a bit disappointed because she obviously had different ideas about having a cat. What can I do to make her more trusting? becomes my mother?