I Think I Swallowed a Textbook
Sadley I can not see Susan, she is projected within your own vision, and in addition, your own mind, giving you complete control. That is why I never have a true idea about what this figment of your own imagination does, for while they are your friend, they are meant to be yours and only yours. However, living in a such a manner at your age is accepteble- in fact, it's inescapable.
This mental visualation, yes, is not real, but do not despair- you may continue to enjoy your fantasy. You are an adolesentant after all- and you must do what youth do. It is far better to imagine than to doubt, so get on with it! Go play with Susan, though take heed, if someone shows disbelief or gets her actions incorrect, you must avoid fighting, and if you can, conflict!
Susan is your own friend, unique to only you, and she appears to only you. Now, go indulge in the activities that you and little Susan enjoy!