I think you need to talk to your partner about how you feel your connection is weakening. You need to spend quality time together and work on the two of you. It's possible she's been lost in her new relationship and you've been feeling rejected.
On top of that, the fact that she wants you to meet someone else, if you are monogamous, must feel like a rejection as well, like she's pushing you away and hoping for someone else to take her place.
I don't think it's a good idea for her to decide that should should meet other people. It's your decision to make. Is it really something you want? Because if you don't, then it's not going to do you (or your partners) any good to force it.
She wants it to be fair? "Fair" is what meets the partners' requirements. It's not fair for you to have to be with someone if you don't want to. It would be more fair for you to have just her, even with the asymmetry.
If you ARE mono, then I suggest you look at some of the mono/poly threads. Also feel free to suggest she reads the forums too if it helps her.
You seem to care a lot about the relaitonship and want it to work and get better. It's possible, but you have to know what you need and want and work on that. Good luck.