Choose the correct option
June is too short to get hold of that branch all by _______.

The correct answer is: Herself

'Herself' is a reflexive pronoun, being the reflexive form of she. It is used the following ways: as an object refers to the same female who is the subject of the sentence.
'June is too short to get hold of that branch all by herself', here 'herself' refers to the subject (June).