Complex sentence: Tina then tells David that she wants nothing more to do with his problems but she becomes involved again after he has a DNA test done on Kylie's new-born daughter, Lily Platt, which proves that David is her father.
Split into simpler sentences: Tina then tells David that she wants nothing more to do with his problems. David gets Tina involved again after he has a paternity test done on Kylie's new-born daughter, Lily Platt, which prove that David is her father.