Complex sentence: Audrey told Casey to keep out of Ashley's marriage and that she was just a fling that Ashley would get over, Casey stressed that her and Ashley were a proper couple and lied saying that her affair had been going on for months.
Split into simpler sentences: Audrey told Casey to keep out of Ashley's marriage and that she was just a fling that Ashley would get over. However, Casey stressed that she and Ashley were a proper couple and lied saying that her affair had been going on for months.