How to hint in a short story that your character has schizophrenia?

For my english coursework I have to write a short story. I have chosen to do mine as a dual narrative, but they are actually the same person. When I handed in my draft to my teacher, she said it was good, but that I needed to make it slightly more obvious to the reader that the character has schizophrenia. How can I do this without making it blatantly obvious from the beginning, but by hinting it so that every person that reads it would think 'maybe they're the same person'?

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).