Even though I'm not a Dom, I'd like to answer anyway, from a sub perspective.

That seems a little harsh to start out with. She's been your sub less than a few days (based on your previous posts about looking), so maybe giving her some gentle verbal correction at first would be the way to give her an opportunity to help herself with this. Then, if after some time passes she still can't control her speech, your idea would be completely appropriate.

Of course, that's just my opinion, based on the fact that slow but firm worked really well with me for my Owner.