From what you’ve saying, I don’t think that anyone at your work knows that you stutter. I know you must feel like that is maybe embarrassing, but why don’t you disclose ? You can say after introducing yourself to the intern something like “Just so you know that if you hear me stutter sometimes, this is normal as I have a speech impediment “ or you might even joke about it if you want. If she is a decent human being she will totally understand. Same for your coworkers and your boss. Trying to hide stuttering is very tiring and will only lead to more stuttering and embarrassment, while being upfront and honest about it will make seem as a brave and courageous person that is not ashamed of his flaws and is working on them. Disclosing is always hard at hard. Best of luck!