Did a bit of googling; apparently she hasn't worked as Mori's assistant, but for what it's worth, she has apparently said that she's a fan of Mori's work
The art in Fellows! in general reminds me of Mori, really -- if they have a house style, I think Kaoru Mori would basically personify it -- but it's true that Sui Sasai (Gisele Alain's artist) draws so much like Mori that you could easily mistake them for the same person. There's gotta be some influence.

