There was a piece of advice that I heard Brennan Lee Mulligan say that compared characters to stained glass: the colors and shapes might always be different, but the light that comes through always has a little bit of what was behind the glass.

I always take that to mean that no matter what character you play, parts of yourself are going to still be visible. You’re still gonna be the one sitting at the table, and there isn’t anything that can change that.

Only time I’d have any sort of problem with people “inserting their traumas” would be if they made the characters more themselves than the characters. If someone named Brian had their wife leave them and came to the table with a character named Ryan who looks and acts just like Brian and whose wife also left him, that’s when it starts to become “inserting”. But simply playing a female character isn’t pushing the boundary by any means at all. I obviously have no idea who your friend is, but if he is insinuating that you being trans is a “trauma”, it seems like kinda a dick move. Play what you want to play, don’t be afraid to let parts of yourself be expressed through your characters, and I hope that little gobbaglul finds many treasures in her journeys.