Hey as dude that was unfortunate to either be born or grew into a stutter growing up mainly being a “block” I understand how stressful having one can be. If she’s older than you or over 18 she should know better. These kind of people that judge others over things they can’t control are very shitty people imo. Family or not I would cut them off or not even bother talking to. You should have a serious conversation with her about your feelings, if she doesn’t change then I would definitely not even bother talking to her.