Removal of conditional green card

I legally adopt a niece (16 yrs old now) . Her green card will expire in about 7 months.
Question: How does my niece file for remove of conditional ? Can she still be include with her birth mother on the removal of condition ?

I legally adopt a niece (16 yrs old now) . Her green card will expire in about 7 months.
Question: How does my niece file for remove of conditional ? Can she still be include with her birth mother on the removal of condition ?