Should I be friends with benefits with her?

Me and this girl, sabrina have been knowing eachother since 7th grade which is 4 years and we always liked eachother also, everytime we're around eachother we end up making out and stuff like that. I want a relationship with her because we get along so well but she says she doesnt want one because she doesnt want to ruin what we have. She says im the only guy she trust and that she'll be friends with benefits with me if i want. But i want more help