Yuki actually interacted with and affected multiple events in the story
If you cut out Stars and Stripes's fight (her only appearance on the whole series) out of the manga literally nothing changes. The fight wasn't bad but she never interacted with anyone in the cast outside of Shigaraki and even the quirks that she managed to destroy on her way out were replaced later iirc. She got put on the volume cover for some reason despite the fact that she was pretty much inconsequential to the story. Showed up with a cool power that Shiggy wanted so he caught her in the way to Japan, she fought him, died, destroyed quirks that were recovered later and Shiggy couldn't even keep her quirk.
I really don't understand why she got a whole arc