Don't get too hung up on how you write if you aren't also considering what you write.
Do whatever you need to do to get through it. The writing will be patiently waiting for you on the other side.
Why is your focus on your friend, and not on the people who are reading the submissions and making decisions about which ones to accept?
Your feelings of envy are harming you by making it hard for you to achieve a degree of self-defined success that might lead to you feeling less envious.
The question is how to go about writing characters who aren't like you, not whether you are allowed to.
We often have to confront the undeniable fact that writing takes time away from other things that we, or other people, think we should be doing.
You have to pace yourself, like an athlete with an injury doing slow small exercises before returning to marathon running.
Work with your innate writing process rather than against it, and you'll be much happier and more productive.
Don't try to tell an "authentic" story. Instead, tell an "inauthentic" truth.
Critiques should not make you question the value of your work, or the value of yourself.