Thank you for your question.
There is no adverse health effect in taking the tablets for as long as she does not want a period. It only becomes a concern if it happens several times a year. Once upon a time we thought progestogens were totally harmless and doctors used them freely. Now we know that high dose progestogen or those used in smaller doses long term through the oral route do have a small albeit significant effect on blood
lipid levels and clotting factors. They also affect cardiac function and breast tissue.
So she doesn't have anything to worry about for a one off treatment episode. Its just not such a good idea to do it very often. The temptation to manipulate periods is great because of hectic lifestyles, increased travelling and activities. So please reassure her and best wishes for your pilgrimage.