Complex sentence: Ringwald was originally approached to play the character of Allison Reynolds, but she was "really upset" because she wanted to play Claire; she eventually convinced the director and the studio to give her the part of Claire.
Split into simpler sentences: Ringwald was originally approached to play the character of Allison Reynolds, but she was "really upset" because she wanted to play Claire. She eventually convinced the director and the studio to give her the part of Claire.