I would test her, start hanging out with other girls and be up front about it. Tell her you want to start seeing other people.
A) It shows her you are not in her back pocket you are still going to be a challenge.
B) Say it after you have the interest of another girl, so she can see that other women want you. Because she will ask who the other woman is...
Those two items are gold when it comes to women. Nothing turns a woman on like seeing the guy they want with another woman, or thinking they are going to lose something for not being good enough. Drives em nuts...
Be cool about it don't be ****y or rude, tell her you are just being honest. Tell her you are sorry and she is still the love of your life.... but you are just going to start seeing other girls. Don't be sad or worried when you talk to her. Always positive, always honest...
A big helper for this strat is to have a decent job so you can romance her a couple nights, then go cold on her and tell her this and stop calling her so much..
She will either step up her game, or give up. It's important to keep in touch with her. Even the break up does not have to be permanent, it's a tool to show her your limits. Just keep it positive, say positive things. Hopefully eventually she will realize what she lost and want to fire things up again so the door needs to be open for her to come back. She has to know that you are still willing to be with her. I'd tell her stuff like "I still love you, but this relationship is not really where I want it to be." say "we can still be friends" alot.