It's gonna be really fucking hard.
Do yourself a favor. Don't do what you normally wouldn't for anyone else for her.
If you truly treasure her, you'll appreciate the bond you already have with her. respect her boundaries. Don't disappear when a new guy inevitably comes in. Don't shame her for her love/sex life.
And as for you yourself OP.... You're young. The love for her is an intense feeling that you probably think you'll feel the rest of your life. You won't. You'll grow older and maybe move away. You'll expand your life and your world. Don't keep your world empty just for her. It'll only lead to so much pain and suffering.
Good luck OP