How about you spend your time worrying about your "Christian witness", and let her worry about hers.
"Who are you to judge another's servant? To his own master he stands or falls. Indeed, he WILL BE MADE TO STAND, for God is able to make him stand."
A Christian is FREE to love God and do as he pleases.
Spiritually immature legalists - so accurately depicted by the SNL "Church Lady" character - just HATE to hear that the sins of Christians have already been paid for.
"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It may be better to live under live robber barons than under omnipotent moral busibodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good, will torment us without end, for they do so with the approval of their own conscience." ~ C.S. Lewis