I am a parent that lost my son on Feb 24, 2005. Michael was 19 at the time of his death and left behind his sister who at the time was 15. Now here we are 14 months later, she's 17 and he would turn 21 next week.
As a parent I know what it is like to suffer a loss, as a sibiling I wouldn't know, all my sisters and my one brother are still with me.
I have watched my daughter suffer and I have talked to her plenty. She has not decided to seek therapy, but I have, not that she is wrong but I have been her therapy on a daily basis. I have encouraged her to make tribute to her brother in anyway that she feels she needs to. I encourage you to do the same thing. Being that this was her only sibiling and now she is an only child, she has inheritated all his belongings and art work, even his guitars. Everything that she feels has meaning she has displayed somewhere in the house so that when ever she begins to feel sad, there is something right next to her that has the identity of her brother. Alot of the things, pictures, art work and even small items that he had in his bedroom are now tokens for her and memories that she has surrounded herself with. Most of the items look like ordinary household things, knick-knacks-brickabrack that everyone would have here and there, except hers have that special meaning to her. She also has may letters and notes that she writes to him on a regular basis, and when she feels the need she takes them to his graveside and leaves them there, I bury mine at his headstone, but she leaves them out in the open because that is what she is comfortable with.
One thing you should always remember is that your pain is real and its ok to have it for the rest of your life. Your sibiling is a part of you and you a part of them. If you die you take a part of them with you as your sibiling has taken a part of you. This is a love that no one can explain to you and you will never be able to explain the love you have for your sibiling. No two people are the same.
It is also ok to walk around with a smile on your face, you dont have to always cry. We are still learning that. It's ok to get mad, and its ok to sit down to eat dinner and start to cry. Cry, scream and greave in the way that makes you feel best, there is absolutely nothing wrong with that and dont ever let anyone tell you differently.
Finding someone to talk to is a great idea, although it doesnt always have to be a professional, it just has to be someone that makes you feel comfortable and helps you in the way that you feel you need to be helped. I dont go to my therapist anymore, because of my daughter and my second husband, they have been my sanity and my rocks. If I ever feel the need to just cry, I do and they never judge that, they hold out their arms, and I dothe same for them. Sometimes that is the best therapy.
Good luck in all your endevors and I hope that the few things I have typed have been able to help you in some way. If you wish to talk more or want to get in touch with me I am on MSN as firstname.lastname@example.org
All my love and prayers to you and your family.