IIRC she said she wanted to be the mo-cap character? I remember her giving an interview before the movie came out where someone basically said the same thing to her and she was like “I wanted to try this type of acting, because it seemed like a rare opportunity, especially for something like Star Wars.” I might be misremembering that, but I do remember thinking something similar before I was told she really wanted to do it, and was surprised.
I think that and she explicitly said she wanted to do mo-cap characters for a bit in big name movies (this and Jungle Book) because she didn’t want people watching a family movie and remembering her role from 12 Years a Slave.
Personally I don’t really get the shoehorned complaints for TLJ. To me, being shoehorned in means having a role that fills no purpose. Maz’s role in TLJ was short and served an understandable, narrative purpose. Considering she wouldn’t have really fit anywhere in TLJ’s story, I thought her cameo was pretty much the one way to include her that wouldn’t have felt shoehorned in. As for TROS, considering we know officially nothing at all about her role, it seems weird to declare one way or another.