Analysis of information sources in references of the Wikipedia article "List of Arthur characters" in English language version.
Your instincts are correct; she is, indeed, a poodle! I'm 99% sure the only rodent-related character is Ratburn.
The Brain is a bear. Binky Barnes is a burly bulldog. (Try saying that three times fast!) Muffy and Francine are both monkeys, and Buster is a rabbit. Sue Ellen is a cat, "'Prunella is a rat,'" Fern is a dog, and George is a moose. The Tibble Twins are bear cubs, and the Read family appears at the front of the animal dictionary. They're aardvarks.
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The Brain is a bear. Binky Barnes is a burly bulldog. (Try saying that three times fast!) Muffy and Francine are both monkeys, and Buster is a rabbit. Sue Ellen is a cat, "'Prunella is a rat,'" Fern is a dog, and George is a moose. The Tibble Twins are bear cubs, and the Read family appears at the front of the animal dictionary. They're aardvarks.
FEATURED ARTICLE: Top Five Things Pal Likes About Fall By Pal Read