Who is Tsaytl from Tevye the Dairyman and the Railroad Stories and what is their importance?

Tsaytl is Tevye and Golde's oldest daughter. She falls in love with a tailor, Motl Komsoyl, and promises to marry him in secret. When she finds out her father has arranged her marriage to Layzar Wolf, she goes into a fit of crying. Her father is unwilling to force her into a marriage that makes her unhappy, and Tsaytl has her own way.