Do you know a how to modify the Imaginary friend made real? Someone told me to use nraas, but I am scared to use it beacuse it's a strong mod. Is there another way?

What do you mean with IF made real? If you want to make it real, make the IF Metamorphium by the Chemistry Table...

She means how to modify how the IF looks after it's been turned human.
As far as I know, you'll need a mod like Nraas master controller or awesomemod that will allow you to enter edit sim mode to do it. Master controller isn't that scary, it doesn't change anything in the game, it only does what you tell it to do, and it's extremely helpful. But if you are unwilling to try it, I'm afraid you won't be able to modify your IF.

With Generations came the ability to send a sim back to CAS. Use the 'testingCheats' code and shift click on the Imaginary Friend. In the ensuing pie menu, there should be an option to modify the sim in CAS. If there isn't, I suppose you're stuck with the Imaginary Friend as it is.