Help with dealing with people who hinder my progress on my stutter

Help with dealing with people who hinder my progress on my stutter I’m a second year student in college rn and my stutter has noticeably decreased in intensity since primary school. I still stumble on words and have trouble pronouncing wounds with multiple vowels in them but I truly think I’m doing better. I recently met a coworker who points out my stutter a lot and makes me feel like I’m not trying hard enough to use words correctly. She imitates me when I mess up a word uses a high pitched voice to tease me. I’ve asked her to stop and she hasn’t. I don’t know how to go about this. I really don’t want to get her in trouble because she’s a good friend otherwise. Sorry this is my first post here and I don’t know how this community works.