I am a US citizen can I apply for green card for her while she is in US and can she stay here while the application is in process?
The answer to both your questions is - yes. But you MUST speak with a lawyer to understand all the nuances of her case.
What is the age the child can apply for a parent's green card?
A child can only apply for a parent's green card upon reaching the age of 21.
During FY 2009 and FY 2010, usage of family-based visas has been exceptionally low, especially among spouses and children of green card holders (the F-2A preference category). In FY 2009, approximately 10,000 family-based visas were unused and, by statute, were reallocated for use by employment-based immigrants in FY 2010.
Mr. Rajiv Khanna, Mr. Kunal Sharma and the rest of the team have been very patient and extremely supportive.
I had filed for my immigrant visa through my spouse, and it was quite complicated. Couple of the other lawyers we spoke to said that there are no chances in winning this case, but Mr Khanna was firm, that the fundamentals are right and thus we have a good chance. Finally, after 2 long years, my immigrant visa has been approved.
What impressed me the most is the Mr. Khanna would immediately schedule an appointment (no charge, of course) every time there was some news from the immigration office or from my side. Even during the final stages, I had asked him a few questions regarding my DS-260 as i was very nervous, he scheduled an appointment immediately and told me exactly what to answer in each question. They made me feel as if I was their only customer. Excellent effort and care for each case by the team, and I would surely refer his firm to everyone.