In reply to Flinticus:
With good management she should be able to avoid a debilitating attack, that management will probably be a combination of medication and listening to her breathing and adjusting activity levels. Hence speaking to the instructor and explaining that she may need to stop it take a break or use her inhailor.
As others have said I'd seriously question the health and safety policy of the company if they don't have first aid trained (incl CPR) staff on-site at all times.
I would maybe discuss some hand signals with the instructor. One to say inhaylor (I need, please get/find it for me), one to say I'm ok (leave me alone to get my breathing under control), and a final one to indicate help (I'm struggling and need assistance/ambulance).
Miming using an inhaylor, a diving OK and a wobbly horizonal wave would be reasonably easy to learn and recognise - as I'm sure you know talking is the last thing you need to do when struggling with your breathing.