I feel a little silly making an assumption, but I think Hypna's better in a fight than she realizes. Whether this is due to a high luck stat, I cannot be certain.
this is a very fun assumption, you are always free to make them :p
She's! Yeah. She is better than she realizes. She doesn't have the confidence in herself at the start because she's not great with guns (that can be improved) and she hasn't actually been in a lot of fights but as time goes on, she naturally gains confidence with experience.
She becomes very focused and determined in a fight, she has a lot of time to make up for and a lot of pent up emotions to work out and a bunch of other things!
Spite is a very powerful motivator, beaten out only by love.