Reesetee, if you meant to say a girl was your girlfriend, but instead called her chubby, she would be offended, regardless of whether or not she was overweight or underweight. You see, these creatures called Women tend to be sensitive about such things.
A reason to split up with your girlfriend? Not a word you'd want to call your girlfriend? Sounds like someone has a problem with people who are overweight. Tame maybe to you, but not necessarily to everyone else.