Originally Posted by yogos
...why would she tell me she'd flirt with other guys if she prefers a monogamous relationship?
Flirting is just flirting. It's not about pursuing relationships, it's just fun to get attention and see a response from others. It can help a person's self-esteem and be a way to practice socializing, too.
She wants to remain monogamous but is obviously glad you won't get all upset and bent out of shape if she flirts with someone else. She's even said she'll flirt in front of you, to make you happy. Why is that not enough for you?
This is a new relationship, just getting started. You are still getting to know each other. The both of you are young. She is underage. You should not be expecting her to have sex with others just to please you.
If you want to continue seeing her, respect her wishes. If you want a cockold relationship where you get to watch your gf have sex with other guys, she is not the one for that. If that is a deal-breaker, then I suggest you look for someone who is of legal age. But keep in mind anyone who participates in that with you should want to do it for their own satisfaction, not yours.