Complex sentence: Megan, realizing that her relationship is stifling her, breaks up with him and goes to Annika's prom, where she tells Annika to be honest and pursue Junior, a friend she has a crush on.
Split into simpler sentences: Megan, realizing that her relationship is stifling her, breaks up with him and then leaves to go to Annika's prom. At the prom she tells Annika to be honest and pursue Junior, her friend who she has a crush on.