Make the next conversation memorable to the coach. Don't worry about what they think of you, just get your point across. You don't have to explain much or apologize. Just tell them not to call your daughter that name. "Hey I know we talked about this previously but Susie doesn't like being called 'coodles'. It upsets her which upsets me. I do not want her called 'coodles' anymore. Thanks, I know you are busy, see you next practice." I'm very friendly with our coaches but they all (current gym and previous gyms) have known I will protect my daughter and that I'm looking out for her best. That's my role in this craziness. If the coach doesn't respond to the next conversation do you really want them coaching your child?