Child stammering are there any techniques I can help her with?

Child stammering are there any techniques I can help her with? We’re in speech and language therapy at the moment she is 6. So far the therapist has given me and my husband ways to help her such as give her plenty of time to talk, reassurance etc. While the advice is great and we are following it she is very frustrated with her stammer and is beginning to hit herself to help ‘get the words out’. The therapist said that asking her to ‘slow down and take a breath’ is bad advice but sometimes it does help if she takes a small pause. Are there any techniques that have helped with a stammer? Like breathing techniques etc. She is such a chatty confident little girl it’s sad to see her start avoiding talking at all because she is getting so frustrated.