Complex sentence: In the 1st season, she and Diego pretended to be a couple so that Diego's father wouldn't find out that Diego is in a band and so that Roberta's mom would leave her alone.
Split into simpler sentences: In the 1st season, she and Diego pretended to be a couple so that Diego's father wouldn't find out that Diego is in a band. And so that Roberta's mom would leave her alone.