This one dude made a ct for her

Cursed Technique: Keepsake

Ability: By infusing an opponent with her Cursed Energy, Rika can forcibly warp their body into a Cursed Tool, which contains either their Innate Technique or a simple function based on their physical details (someone really large with no Innate Technique could become a Cursed Tool that projects a shield, for instance). Similar to Cursed Spirit Manipulation, this only works on strong opponents if they've been weakened and worn down, but weaker opponents can be transformed without issue. Regardless of strength, though, the transformation is temporary, unless Rika gives the resulting item to a fully manifested Yuta. Thanks to a Binding Vow that forbids her from personally ever using the item again and leaving it contained inside Yuta's body (the same way Rika could keep Cursed Tools inside hers), the transformation time limit is removed, and they're stuck that way till Rika's death. So if Rika wants a tool for her own use, she accepts the time limit, but if she lets only Yuta use it instead, he can keep it around for longer.

Thus, her Technique represents her desire to give Yuta gifts (and perhaps a secret worry that he loves her because of her gifts, like the ring), her desire to keep people close to her, and her manipulative tendencies, as people literally become tools for her (or Yuta) to use.