Hi, when you use the change_scene_to_file function, you are NOT using the instance stored in the profile_scene variable. It becomes an orphan node. Also, since you never add the profile_scene instance to the tree, the @onready variables are never initialized because that only happens after the node is added to the tree.
There is not need to instantiate the girl profile scene if you are using the scenetree change scene function. Instead, you can use autoloads to pass information between scenes. Or you can not use the scenetree change scene function and instead add the profile scene to the tree yourself. Make sure to only call the update profile function after it is added to the scenetree, though.