Complex sentence: Rose grudgingly allows Maggie to move in with her when their stepmother throws her out of the house, but their already difficult relationship ends when Rose catches Maggie in bed with Jim (Richard Burgi), her boyfriend.
Split into simpler sentences: Rose grudgingly allows Maggie to move in with her when their stepmother throws her out of the house. Their already difficult relationship ends, however when Rose catches Maggie in bed with Jim (Richard Burgi), her boyfriend.