Cheering up my Sister! Please help me, this is really important!?

Hi, this is Chris Ram the owner of this account! So I am in a very serious situation here and I really need some help, support, and advice too. My 2nd Cousin who I consider and who basically is my little sister Selena is a 15 year old beautiful girl who is gonna graduate junior high school in a couple of weeks. The problem is that her mom is leaving and she is going back to Canada in a few days and Selena's formal is coming up & her mom is not going to be there for her. Selena has had a very hard life, I mean she grew up without a father whom she only talks to on the phone because he runs his business in Guyana in South America. Selena has been crying all the time and I feel so bad. I have been crying a lot too because she is my best friend and her and I are very close. We were both born in December, Selena was born on December 26th and I was born on December 27th. I bought Selena a dress for her formal and another dress for her Friends quincenara coming up in a month. I have a lot of money saved up and I work at a high paying job plus I live with my parents so I have no bills to pay for or anything except my car every month. Every week I give Selena money and I take her to buy clothes, jewelry, shoes, and girl stuff all the time at Wet seal, D & W shoes, Claire's, In Maple Grove and the Maple-wood Mall. I told Selena that I love her with all my heart and that I will always be there for her. I told her that she is my best friend and I love her more than anyone else in this entire world and that I will do anything for her. Selena really needs and older brother in her life and I thank god all the time because I always wanted a little sister ever since I was a kid. But please give me some advice on how I can cheer her up when she is crying and what else I can do for her. She has been crying a lot and I want to help her. & Girls How would you feel If I was your big brother? Please help me help her. Thanks so much!