I think you should consult her general physician or family doctor about this. I mean maybe it might aggravate her asthma or maybe it wont. If your only concern is medical then its better to talk to a doctor who has been seeing her for a long time who knows her history.
Other than that, if she can happily move to canada its fine. but then she wont able to keep her job i assume? What does your daughter say about this proposal?