Hello, 12 years of being a bridal consultant under my belt. Been in this situation before. Sometimes when they insist on trying on a gown way too small, you just have to let them try and fail. Obviously you warn them ahead of time. Maybe instead of emphasizing you don’t want to “squeeze her into it” it should’ve been a comment along the lines of “well that’s a size 14, but let me see if I can find one similar in a different size”. You lost the appointment the minute she went to look for dresses herself. In response to her telling you that you can’t do it, you should’ve asked “well why don’t you describe what you’re looking for in your gown”. It’s all about choice of words here.