Marnie, but it is tentative. The problem with the Galarian characters for me is that they seem unoriginal. Hop is Hau with a more developed arc, Rose is Lusamine with a missing brain instead of a poisoned one, then there is the secondary villain devoted to them (Oleana and Guzma). They even both have a child working with said secondary villain - Bede and Gladion. The parralels between Team Yell and Team Skull need no examination. Piers has traits from both Guzma and Gladion, which would make Marnie the Lillie copy, but I think they did a good job giving her a distinct appearance, personality and arc, if it was a little underdeveloped.
I am obviously summarising a lot, and am aware that they are not copy-pasted, but it is something that has bothered me since I started my completely blind playthrough and thought 'huh, this Champion reminds me of Kukui, and the rival is very Hau-ish'.