"Oh!" Clara's expression turned immediately stricken. "My apologies, I wasn't thinking," she said contritely. "I know some excellent spells to remove stains so let me do that, to make up for my mistake."
The arrival of the Muggle put an end to the apologies, however, and Clara regarded the woman with the expression of someone who'd just seen a particularly disgusting slug - which was precisely how she viewed the creature. "Yap, yap, yap, like dog, like owner," she smirked and cast a silencing spell on the woman.