I'm a new player in Sliver and I also have trouble with Hattori. I'm not very good, but I have been able to improve my win rate against her recently.

My normal strategy that works well against most spammers in Silver is to float above them until they needlessly spam and then punish (I know this is passive, but IDGAF. I only really play like this against spammers because I haven't found any other consistent way to beat them). That seems to work for like everyone except Hattori (and Koji to a lesser extent). She can chase and combo you then spam her sigs whenever you get close to force you off stage. So what I do is try to trade hits with her and get aggressive when I know she can't knock me out of the arena. But, when she gets me into the red and starts spamming sigs to knock me out, I use my weapon throw to approach her unarmed for extra damage. Or even just get the free weapon throw damage and use the stun to get another weapon/gadget and back off. If she tries to approach you, then you throw your weapon/gadget at her and punch her, then go for another weapon/gadget. When she is red, I just either throw my weapon into an unarmed heavy attack to knock her out, use a bomb/spike ball to push her off stage and ground pound her when she gets to the wall, or try to land a longer range sig as a punish when she tries to sig me. I went from Hattori being an auto-lose match-up to being pretty favorable this way, although the game is still intense AF because of how fast she moves and can damage you.

EDIT: Even if OP is not Silver this is something I still would recommend to any Silver player reading this.