How does a woman avoid showing off (riya') in supererogatory (nafila) prayers, especially if she does not regularly perform them in private and feels that her attempt to commit to them in front of others might be a form of showing off?

We advise you to maintain supererogatory prayers in solitude and in public, and do not abandon them for fear of falling into showing off (riya'); for this is one of Satan's tricks. Rather, perform acts of obedience and be sincere to Allah, and do not abandon obedience out of fear of showing off.