Agree with lots of the points below, and another point to add… she may just not be emotionally and mentally ready to try and improve her stutter. From my personal experience and watching my younger sister, around 11-14 yrs, I didn’t want to address it, I wouldn’t speak and would avoid speaking at all costs. 14-17 I was in the mindset of “I need to be fixed” and went to speech therapy for all those years. Yes there was some improvement but not a lot. It wasn’t until 18 when I found a support group that I realised that is completely ok the stutter and that I don’t need to be fixed or saved. I just don’t think that surge of motivation has hit her quite yet, she isn’t annoyed or that upset about it yet that she is willing to do ‘whatever it takes’ to work on it. It may come, it may not, but keep being a super mum and supporting her as much as you can. Just be there for her and she will realise it one day. Hope everything works out! <3