But please we wary of prednisone or inhaled steroids. The side effects can be very nasty and they almost killed me. There are natural anti-inflammatories available that work just as well. Naturally the pharmaceutical industry does not promote them. Albuterol inhalers and anti-histimines are very helpful. The former works quickly to abort an attack.
What you describe does suggest that Asthma is the most likely diagnosis, worsened by the volcanic ash. However, there are many other irritants and allergens that can cause activation of underlying asthma. And, there are other lung diseases that can masquerade as asthma and it sometimes takes an Allergist or Lung Specialist to distinguish these diseases from asthma. You describe her school as being located in a zone that is in “a moist yet windy environment with clean air, not coming in from the volcano.” Yet, her most recent attacks “both started about 11:00 AM at her school.
Two things to keep in mind regarding asthma attacks: 1) Such attacks may not occur immediately following exposure, to either an irritant or an allergen and these are called delayed reactions or responses. Some attacks can occur as long as 4-6 hours after exposure, so as you suggest, the onset of symptoms at school could have been a reaction to something she was exposed to in the village or on the bus, including the possibility that she is now riding in a different bus; one that contains substances not present in the previous bus or a bus with a different ventilation system. The exposures could include such things as animal dander on the clothing of her fellow students on the bus or perfume worn by some of the girls on the bus. She could also be reacting to something at the school, other than volcanic materials. Perhaps, reacting to some substance newly introduced into the air at the school. A common example of this would be substances released from the interior of the walls or roof of a building, in the course of remodeling and, 2) Not all materials, including but not limited to those spewed out by volcanoes are visible. Gases, especially, can be invisible.
Finally, asthma is a disease that runs in cycles; often present in early childhood, then seemingly gone during adolescence, only to return in adulthood. Or the opposite. That with adolescence and the beginning of menstrual periods, some girls will experience a worsening of asthma around the time of their menstrual periods.
I suggest two things to sort all this out: 1) given the severity and seriousness of her recent symptoms, she should be seen by an asthma specialist, either an Allergist or a Lung Specialist and, 2) her asthma should be treated as necessary, to gain complete control of it and complete or near-complete relief of symptoms.
Good luck