What should I say about my cousin coming to live with my family?

My second cousin (let’s call her Charli) is living with my aunty (lets call her Karen) (her great aunty) because of family problems, but Karen treats Charli badly and makes her feel unloved. Charli is 14 years old and in year 8 and all she really wants is to be loved. She thinks that the only way to get the feeling of being loved and wanted is by being boy crazy. Everything she does has to include a boy, recently she has ran away from home with her 21 year old boyfriend and is living with him.
Mum and Dad gave Charli the option to come live with us for the rest of her life. In other words my parents foster her. My parents asked me and my siblings what we think about it and if we want her or not.
My older brother said ‘she’s family and we cant just leave her how she is now, it would be good for her to get out of where she is’.
My youger sister said ‘yes! that way I can have another sister!’
But me, I’m not sure, I would love to have her close and I understand she needs to get out of where she is, but I think I would get very sick of her quite quickly but I know I will get used to her. Plus she will be at the same school just a year below. The good things about her coming to live with us is that I can be closer to her and I get mum and dad’s big room so she can have mine and it will be like having another sister. The bad sides is we will get sick of each other and I love to have my own space as well as my brother will be leaving home soon and then I will be the one to take care of her at school and when we are out.
If you were in my situation, what would you do?