I think it’s important for your friend to see a speech therapist with knowledge in this area rather than following online videos as they might risk causing further problems. Speech therapy in my experience is mainly successful with vocal cord paralysis and patients can be very surprised at how well it works.
Also important not to wait 9 months! Gosh that’s a long wait and can lead to certain behaviours developing as a compensation, causing more problems.
I would be happy to chat to this person and can offer virtual therapy sessions with exercises for home practise following assessment.