Senior US Citizen adopting foreign adult

Hello. I know of a Chinese old lady who is over 80 years old now. She is a U.S. citizen who resided in DC and/or NY. She has no husband or children. Recently she has been considering of adopting a young lady from China. The young lady is a 23-year-old who has been close to the old lady's family. The young lady's mother was a long-time student under the old lady's sibling decades ago. They are not related by blood, but they had lived together a long time ago.

My questions are:

1. Is it possible for the old lady to adopt the 23-year-old foreign young lady if both parties consented? What documents or evidences do they need to show?

2. If the young lady wants to come to the U.S. to stay and take care of the old lady, how could she do so? Would she be eligible for applying for a green card or does she need to apply for a certain visa? How does the naturalization work for the young lady in this case?


Please contact me soon. Thank you.