Not doing my respiratory treatments didn’t occur to me.
There were two periods in my life regarding this: up until I was about 25 I did not know of this, no one told me that this was an option or an advisable treatment. Then I started working with a nebulizer after switching hospitals because I moved to another part of the country and my new pulmonologist suggested I might try this and find it beneficial. This was for once a day, in the morning.
I immediately noticed the great advantage it gave me, not having to cough for the rest of the day or night, when concentrating the cleaning in this morning session, and having more energy and air. So I stuck with it, although in the beginning of course this changed my morning habits considerably. But I integrated it well, using this time to watch the morning news on tv and mostly to meditate.
After 2 years I needed to start inhaling antibiotics and this required me to add a (shorter) evening session. This was no problem integrating in the evening. I watched the evening news on tv, or listened to music, or meditated.
Since then, I never had the luxury of skipping either of these sessions, not even after stopping the inhaled antibiotics after 25 years – I even needed the evening session anyway to protect a good night’s rest.
I think this is the crucial point here: it would be difficult to maintain this routine if there were not a clear and immediate advantage to be achieved and an intern motivation to stick with it. The practical implementation comes last, after this.
Since your friend seems to be able to skip the routine for months (or even longer?) without choking or severe decrease in lung function, she either does not feel any immediate and clear benefits attached to the routine, or there are benefits but she is willing and able to forfeit them in exchange for more freedom. Both situations could lead to the legitimate choice not to pick up the routine. She is the only one who can determine this balance. But there is a caveat.
She has to look into herself to determine if the motives she has for skipping routine and not picking it up, are (still) valid and honest and true in her own opinion. It might be that the only problem she has with her choice is feeling guilty because some one told her that she should do it, and she just feels bad not obeying that; then she just has to get rid of this guilt and feel free treating her body the way she wants to.
But she should look for a genuine intern motivation to do the treatment. If that is not there, nothing external can be done. Sometimes however the motivation has gone because the patient suffers from a general lack of motivation or aliveness, perhaps a hidden depression or wrong negative convictions about the body and life. Perhaps she is unconsciously hurting herself on purpose by not doing the required therapy. If this is the case, she might need psychological help to reveal the intern dialogue she has with herself, that keeps her stuck. After cleaning that up, she can make up the balance again and decide what feels good.
If, with or without help, she finds this motivation again, there are lots of practical things she probably already knows very well, that make it easier to start and maintain the routine. You mentioned a few as well. Incorporating the treatment in the daily routine is important.
In my case, I never felt it was a waste of time. It allowed me to go through the day with enough air and more energy, without coughing and I used the time to meditate as well. Even in times of great mental distress, I had no problem maintaining the routine. In a way, the routine even helped me through the day, providing at least two moments of getting out of my mind and a strong reason to get up in the morning (besides choking and needing to walk the dog). It also gave me a sense of accomplishment, having (at least) completed my routine and taking care of my body, which made me feel better about myself when I needed this the most.