Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
We thank our sister for her adherence to the Sunnah and her being worried for her failure to do it. This is indeed a sign of good faith (Iman) InshaAllah.
As for sleeping on the right hand side, it is Sunnah as you mentioned and one should endeavor to abide by it. But when the person does his best to adhere to it and fails to do so because of difficulty or hardship, then he/she can sleep on their left hand side.
Allah Says (interpretation of meaning): "...and (He) has not laid upon you in religion any hardship."
On the other hand, sleeping on one's left side is not forbidden.
Allaah knows best.