I emailed Michael Mallory, author of the Amelia Pettigrew (Watson) mysteries, which have been published over a period of at least six years to ascertain whether he would be bothered by the minions producing Amelia Pettipants stories. His response:
From Kate's and your description of the character, she doesn't sound much like my Amelia (mine, for instance, is not a spinster; in fact, her original "hook" was the identity of her spouse), and I don't have a copyright on the name "Amelia," so I don't see a problem. (For the record, I took the name from an old television film, "There's Something About Amelia.") You may, however, want to be aware of the Elizabeth Peters (Barbara Michaels) character "Amelia Peabody," since she is much more visible in the marketplace.
And, as reported by Kate, Mr. Mallory has publicly bragged about having inspired Amelia Pettipants. I believe we're cleared for takeoff, and I hope anyone who was previously concerned will now join the fun.