I think the A-levels route, they tend to be regarded slightly better than BTEC's and provides more scope for the future as you said.

When it comes to Uni if not 100% decided I would advise anyone to take a year or two out and travel/work abroad, that extra maturity and time to decide between 18 and 20 is huge! I have worked a Ski season in Italy and worked as a sports coach in camp america, both were the best experience of my life, made friends for live from all over the world. Sounds as if this would really suit her as she already teaches sports.