1.It's up to everyone to decide what is right for them.
It是形式主语,不定式短语to decide what is right for them是真正的主语.
is up to everyone是系表结构,做句子的谓语.
不定式中,what is right for them是decide的宾语从句.
2.三楼解释基本正确.
She是主语；
was looked after是谓语；
by her mother是状语.