US Immigration from Saint Lucia

I am the sponsor petitioning for my husband who is currently in the US seeking AOS but he has a 17 year old daughter who is currently living in his home country and I want to also petition for her to obtain a visa tor permanent residence in USA. I am a bit confused about how to complete a section on my i 864 form, specifically the questions in part 3 asking whether she would follow within 6 months or after. I would like to file along with my petition for my husband. Is this possible to include her on my i130 petition for him or do I need to submit a separate form for her solely since she is not currently in the USA?