My mom told me my cousin was saying some pretty mean things about my boyfriend this past weekend at her birthday party.  It has really upset me because she is talking about his looks and not his character and not only is saying mean things about him because my mom likes him.  I want to text and her and let her know that she has hurt my feelings for taking unnecessary jabs at him and that I am disappointed in her.  She's in her 50s, I think the last thing she needs to worry about is my boyfriend's hairline while we are not even present for her to say it to his face.

WIBTA if I told her how I felt?