re: I need some honest relationship advice

Yep, that's the idea.

I would like to add that I don't understand the advice to "make a clean break" or "break up with your GF" because I don't agree that OP is in a position where he's compelled to break anything or stop being associated with anybody.

The nature of his relationship is going to change. It's going from a high school type of "going steady" to something more mature and open.

She wants some freedom. Let her have it and enjoy some freedom too. No need to say "hey, let's break up" or "let's have a clean break". Just say, "our relationship is more mature and is now OPEN so that we can experience new things with new people".

They could still end up together some time in the future 1, 2, 3 or 5 years from now -- who knows?

Why close doors and burn bridges?

That's my 2 cents.