Complex sentence: At the Wedding rehearsal Jennifer's sister gives a heart felt speech which drives Jennifer to leave the room and confess to Vince that she can't go through with this, and can't marry a man who doesn't love her.
Split into simpler sentences: At the wedding rehearsal, Jennifer's sister gives a heart felt speech, which drives Jennifer to leave the room. She confesses to Vince that she can't go through with this and can't marry a man who doesn't love her.