thx. this is how i feel inside and i wouldnt want to offend god or christ by full well knowingly going against my faith. at the same time i think im going to go speak with my priest so i can get some religious counseling on the matter. i may not attend this event but i still love my sister and i djont want to write her off yet.
You're in a tough spot. Be as gentle as you can but do explain to her that you will not be participating and you do not approve. You can even say, "These are the edicts of my Catholic Faith." Gently explain to her exactly what mortal sin is and also tell her that the Catholic faith has been under attack from numerous enemies for 2000 years.
Believe it of not, a lot of youngsters today think that the Church had a free ride with nothing but peace and joy (spiritually we did!) and that they are the first generation to have the mental wherewithal to question Church doctrines. Actually, this generation is the 874th in line to think these things.
However, you are in a tough spot. I hope you stand firm and refuse to participate. Still seek the advice of a priest but you know you can't stand by and give the impression to others that a lesbian marriage is in any way acceptable.