Given that Mrs. Maia’s role in the movie is limited to the incident with Ducky, expressing disappointment about the inexplicable drying up of the waterhole, and concurring with Mr. Threehorn (and an anonymous Lambeosaurus) that Doc appears to have brought bad luck to the Great Valley, we don’t know that much about her personality. (Heck, she’s such a minor character, she doesn’t even get a voice credit! :blink:) However, since she comes off as grouchy and disagreeable (though I thought she appeared relatively calm at the waterhole scene) in the little screen time she does get, it’s not difficult for fanfiction writers in need of a leafeater villain to take the extra step and turn her into one.
While I agree that Mrs. Maia’s treatment of Ducky was overly harsh, I’m personally not convinced she’s much worse than Mr. Threehorn. I wouldn’t be surprised if, like him, she’s one of the more speciesist Great Valley residents. Maybe I’m imagining things, but I thought the expression on her face as she was picking up Ducky looked a little...disgusted, like she was handling something unpleasant. (I could be wrong, though; looking at Mrs. Maia’s appearances in the movie, she almost always seems to have that scowl on her face.)
It also occurs to me that Mrs. Maia was sleeping at the time Ducky intruded on her nest, and being woken up probably aggravated her irritation at what she regarded as a potential threat to her eggs. (In Ducky’s defense, I’m certain she wouldn’t have caused the eggs any harm, being both very light and extremely considerate about egg safety, but Mrs. Maia probably didn’t know that.)