Ivory Religion Chiffon Maxi Dress

EUC worn once for an event. No rips, stains or snags. Ivory chiffon Religion spaghetti strap maxi dress. Long and would be good for high heels. Underlay is a short cotton mini dress, overlay has flowy chiffon strips running down the legs. Size Medium? I think it says 12 but fits more like a 6. I usually wear size 4 and this fits me just a little loose. Would be gorgeous as a bridesmaid or engagement photo dress!