Hello anon don't worry I'm 5ft7 and 118 and I'm not underweight? I am at the low end of the healthy bmi range I know that but not dangerously thin. Your friend obviously doesn't need to lose weight but I can understand how she couls feel 'fat' because I felt fat at 115, what she maybe needs to do is workout and tone up and focus on what she looks and feels like instead of a silly number! Hope you can talk to her :)