As a dog who loves attention, but doesn't like it when people think I'm a boy.. I'm going to speculate that this Bulldog isn't in on the joke. Therefore, I'm going to say "grrrrrrrrr" for her.
At the same time, you have to wonder, does she know she's got a stache? Is this part of her Sherlock Holmes costume? Is there tasty food caught in the mustache, like a real one? Is that why she likes it? BOL What do you think? Do you have one?