What Does Breathlessness During Sleep Indicate?
Possible sleep apnea.
Detailed Answer:
I read your question carefully and I understand your concern.
Reading your description the most likely diagnosis seems to be sleep apnea a condition where during sleep the walls of her upper airway collapse and breathing is temporarily interrupted. Apart from the episodes that you describe people with sleep apnea usually have a tendency to snore during the night and more importantly feel tired and sleepy during the day, not refreshed at awakening after the night sleep.
Most commonly it happens due to obstruction in people who are obese, but there might be other predisposing factors such as abnormalities of the airways (large tonsils, small jaw etc) which narrow airways, use of sedatives and alcohol.
It requires medical attention as apart from the those symptoms it puts the patient at risk for conditions such stroke, heart attack, abnormal heart rhythm, and high blood pressure.
Apart from the above symptoms the diagnosis is usually confirmed by sleep studies called polysomnography.
Treatment after diagnosis confirmation depends on cause, lifestyle changes such as losing weight, quitting alcohol, smoking, treating allergies and nasal and tonsils issues. If those aren't enough some aiding devices to keep positive airway pressure during sleep can be used or oral appliances.
I remain at your disposal for further questions.