Complex sentence: Sonya, the Professor's daughter by his first wife, who has worked with Vanya to keep the estate going, meanwhile suffers from the awareness of her own lack of beauty and from her unrequited feelings for Dr. Astrov.
Split into simpler sentences: Sonya, the Professor's daughter by his first wife has worked with Vanya to keep the estate going. She suffers from the awareness of her own lack of beauty and from her unrequited feelings for Dr. Astrov.