How can I get my pet mouse to be more social?

I recently bought two mice, and I want them to be social with humans and not be afraid of being held or pet. I’ve been successful training one of the mice to trust me, and she now runs into my hand willingly if I lower one into the cage. The other mouse, however, is still very nervous and runs into their little house when anyone comes near the cage. The only time I managed to get a hold of her, she was very frightened and ended up biting my hand, so I put her back in the cage and didn’t bother her for the rest of the day. But since then, I’ve been trying a couple times a day to get her to sniff my fingers or take food from my hand, but she seems just as nervous as ever, even though the other mouse seems to love human interaction.

Is there anything I can do to make her not be so afraid of humans? I’m unwilling to try to catch her and hold her again since she seemed so frightened the last time, but I can’t think of any other way to get her used to being held by humans. I’m also worried because I’m going to have to clean their cage soon and I don’t want her to get stressed out and possibly harm herself when I have to move her into their plastic ball. Any tips?