Complex sentence: Her mother Bonnie Plunkett (Allison Janney) is also a recovering drug and alcohol addict, as well as her 17-year-old daughter Violet (Sadie Calvano), who was born when Christy was 16, has become pregnant by her boyfriend Luke.
Split into simpler sentences: Her mother Bonnie Plunkett (Allison Janney) is also a recovering drug and alcohol addict. Christy's 17-year-old daughter Violet (Sadie Calvano), who was born when Christy was 16, has herself become a teen mother by her boyfriend Luke.