Sponsor my sister to come to USA

I am a US citizen and sponsored my sister to immigrate to USA. It is Family Fourth Preference (F4): Brothers and sisters of United States citizens, and their spouses and children.

She will get the visa next year. My question is which form I should use to add her hu*****and and her daughter (she is not married)? What is the age limit for her daughter? A lawyer said my sister would fill in a form for her family, not me.

Thank you very much.