Maybe... I would first continue to encourage my daughter to be the one to speak up and politely offer that she hears what the coach is saying, but she is not understanding HOW to make the correction. Encourage her to ask "Can you help me better understand how to make a smaller bridge? What should I do exactly? Can you show me?"
If you have been trying this, but child is already asking and not being successful, or child is highly resistant and not bold enough to speak up, and this is serious enough to be affecting your child's enjoyment of the sport for weeks on end, then it might be time for a 1 on 1 with coach.
If you do speak with the coach, I would suggest the topic not center on this bwo skill and specific correction issue (high interfering cgm risk!), but more generally about your concern for your daughter's attitude (frustrations) about gym, and asking the coach's perspective on how she is taking corrections, etc., how her attitude in class has been, etc. If the coach is receptive to a conversation and listening, then it might be ok to share that your daughter gave you an example of something that frustrated her (the bwo thing) in the interest of just providing more color to the picture.
Otherwise, if this isn't systemic, and it's just this one skill that is giving her trouble and she's not 'in the dumps' about gymnastics in general and ready to quit, I would let it go for now.