Complex sentence: This upset Gail, as she was estranged from Sarah, as she felt she was being replaced and cut out of Bethany's life when she was there from the beginning and had looked after her whilst Sarah was at school.
Split into simpler sentences: This upset Gail, as she was estranged from Sarah, as she felt she was being replaced and cut out of Bethany's life. She was there from the beginning and had looked after her while Sarah was at school.