What do I do?

My little girl (5 years old) came home today, out of the blue, and said she wanted to be a boy.

She told me to throw away her barbies and give her Ethan's (her brother's) old clothes.

When I asked her what made her want to be a boy, she said it was because she could.

She has never previously mentioned anything about wanting to be identified as a boy, and it was so random.

What do I do? What if it's not a cute little "phase?" I mean I'm not going to let her cut her hair and get rid of her dresses if she's going to change her mind in a week.

But I also understand that people have discovered their identities at this age as well.

Advice?

EDIT:

she asked me if I could take her to cut her hair. Also, in no way is expressing your identity a phase or a lifestyle. I'm just wondering if she is truly expressing her identity.

EDIT TWO:

She changed her mind today πŸ˜‚. She now wants to be a cat. I'll just let her be herself! Thanks for all the advice 😘😘😘