Grillby, noo...
In this picture, she's showing them how to say "asshole". Papyrus is trying to copy her (success rate... not looking good) and Sans is just watching and learning. Ah yes, such good influences the skeleton brothers have...
This is Grillby IV as she appears in BTA: a teenager. She is sixteen. Technically, this is not her first job, since she helps her dad (Grillby III... It's easier to keep naming heirs "Grillby" than changing the name of the restaurant) at the restaurant. But this is the first one she's being paid for!
All of the Grillbys are proficient in sign language, since fire can't talk. Don't think too hard about that, the Grillbys aren't much more than a bit XD