Perhaps it is time to tell your parents about Jeanette. I think they will be able to help and advise you on how to fix this relationship. Do you have any really friends? If you have a Guidance Counselor at your school, that person may be able to help but tell someone.
Peace and Love,
You've tried to get rid of her yourself and have been unable. In my opinion it's time for you to get rid of her. and therefore it's time for you to be open with an adult that can help you do that.
You have a busy time ahead of you with school and then post secondary school. (if you want to get ahead in life) You don't have time to have any head games going on. Your free time away from studies should be spent with real live folks , that you can invite to your birthday party or your graduation of wedding. If you need help to make real friends, then the therapist that you talk to about getting rid of Jeanette.
You say she wears green clothes. and you've seen her since you were about 4 or 5 years old ? Where do you see her? Is it only in your house, or is in school or anywhere you are when you think of her?