Correct Answer: I told you that you should believe her.

Solution : The fourth option is correct.

Explanation:
Indirect form, also known as indirect speech or reported speech, is a way of expressing someone else's words or statements without quoting them directly. In indirect form, the speaker reports or paraphrases what was said by another person, often introducing it with a reporting verb or phrase.

• The reporting verb said changed to told .
• The pronoun "to you" changes to "you".
• The modals should remain the same.

Therefore, the indirect form would be: I told you that you should believe her.