Complex sentence: Leslie suggests that they call Ben with the baby monitor and pretend to have reconciled, but they can't come to an agreement about what to tell Ben, and ultimately break the baby monitor--effectively locking them in the office until 8.
Split into simpler sentences: Leslie suggests that they call Ben with the baby monitor and pretend to have reconciled, but they can't come to an agreement about what to tell Ben. She ultimately breaks the baby monitor, effectively locking them in the office until 8.