I'm sure good intentions that sent her home to soreness and stiffness that lasted for days. It just added to her already stressed out state. Soreness makes it more difficult to breathe. In addition, when you push the body and constrict the chest you make the heart work harder than it needs to. I believe this can exacerbate heart conditions.
Workouts just take a little longer, that's all.
This may be helpful to see if the trainer is open to new information. I've a weight training workout regimen outlined in the workbook. It only addresses breathing so there will be plenty to learn from them in conjunction with that. This accent on sound reproduction ensures that the internal sensing of the breath is replicatable and measurable. If you can breathe right you can sing but if you sing you do not necessarily breathe right.