I've seen photographs of a kind of overshoe for a 1790s Louis heel dress shoe in the Kyoto Museum book "Revolution in Fashion" - the example there was of a matching embroidered overshoe which slipped on over the daintier dress shoe, presumably for protection.

Perhaps Mrs. Allen had some sort of canvas or sturdy fabric overshoe like this to protect her fancy shoes whilst traveling.

Louisa
Mistress of the Garderobe