Correct Answer: Mother told her to paint the river blue.

Solution : The correct choice is the second option.

The indirect form involves reporting or conveying someone else's statement or request without quoting the exact words.

The steps of conversion are as follows:

• The reporting verb "said" in the direct speech is changed to "told" in the indirect speech, as it is more appropriate for a directive or command.
• The pronoun "her" remains the same as it refers to the same person.
• The imperative sentence "paint the river blue" is transformed into the infinitive phrase "to paint the river blue".

Therefore, the indirect speech would be: "Mother told her to paint the river blue."