(Question)Which do we use as an objective complement, an objective case or a subjective case? And would you let me know some examples?
1. I think the girl she.
2. I think the girl her.
(What about these examples?)
The subjective pronoun is "she."
The objective pronoun is "her."
Neither of your sentences makes sense as you posted them.
The correct sentence would be "I think the girl is she." However, that sounds awkward to many of us. A better construction is:
I think that she is the girl.