Complex sentence: Her mother had intended only for her older brother Buddy, who had already achieved some success as a child actor, to try out for the part, but took Jodie with them to the casting call, where she was spotted by the casting agents.
Split into simpler sentences: Her mother had intended only for her older brother Buddy, who had already achieved some success as a child actor, to try out for the part. She had however taken Jodie with them to the casting call, where she was spotted by the casting agents.