Of all these people, I'd like to be friends with her the most.
Among all these people, I would choose her as my friend before anyone else.
ーOf all these people, I'd like to be friends with her the most.
「この人たちの中で、彼女と一番友達になりたい」
of all ... で「…の中で」
to be friend with ... the most で「…と一番友達になりたい」
ーAmong all these people, I would choose her as my friend before anyone else.
「これらの人たちの中で、誰よりも彼女を友達として選ぶ」
among all ... で「…の間で_
to choose で「選ぶ」
before anyone else で「誰よりも先に」
ご参考まで!