Complex sentence: At school, Hedvig avoids Bobo and Klara; they think that this is because she regrets having her hair cut and is angry at them, but in fact she is embarrassed by her mother's behavior and assumes that Bobo and Klara are angry at her.
Split into simpler sentences: At school, Hedvig avoids Bobo and Klara; they think that this is because she regrets having her hair cut and is angry at them. She is actually embarrassed by her mother's behavior and assumes that Bobo and Klara are angry at her.