Would you like some hot apple NO.
As i said elsewhere to someone after reading all this:
My first gf could have been a carbon copy of this girl. I eventually got my head screwed on properly and kicked her to the curb, only to have her contact me years later looking to become friends again after an experience beating cancer. Her claim was that she had learned what the important things were in life (and that i was The One That Got away); but the truth was that she had just learned how much more she could manipulate people, without the bother of even having to use sex to get her way.
Toxic people rarely outgrow their toxicity. You need to tell this girl that she's damaged goods, and find someone who understands that relationships are a two-way street. She's controlling you, and it's clear that she's decided that for you to have the 'privilege' of being involved with her, that you MUST follow every rule she makes up. The point of you having a two-year period is nothing more than a manipulative control test. When she sees that you'll follow her rules willingly, don't be surprised when at the end of that two years she decides you're still not allowed to have others, based on her insistence of "You just don't know how to be poly."
*She's using your lack of experience as a weapon against you. Rather than giving you the freedom and respect to actually learn these things through trial and error, she expects that the knowledge will somehow pop into your head via osmosis. Sorry, it just doesn't work that way. Further, this lack of knowledge and experience is being taken as a deliberate intent to "violate the boundaries" of your relationship with her.
*Not only has she not given you any input or dialogue on where those boundaries are; she's been actively moving them on you specifically to allow her to interpret your actions as having violated them. Her telling you that Making-out was allowed (then accusing you of cheating) is another test to show how devoted you are to her. It's designed to determine how much spine/willpower you have, and how you handle her decision that you've "wronged" her. In order to "Pass" the test, you'll have to submit your will completely, and accept her word as Truth. Those "two years" will turn into seven, or 20, of "Making it work" with her. In fact, i'm really starting to doubt if "Girl B" is really into you at all; she may well be an active participant in the test. Should you choose to dump the g/f and pursue B, watch out for this. It could easily be a routine that the two of them worked out together to help fill their lives with boys they can control.
*Giving you cited proofs in her letter that her actions do not constitute abuse is nothing but a diversionary tactic. Abuse is not defined by hard-and-fast parameters. Manipulative behavior is definitely abuse, regardless of how much she might try to argue against it. You have a right to your feelings and reactions; and nothing she can say or point at can make them "wrong" or "Incorrect".
*Something i decided years ago: I'd rather be happy than right. If taking ownership of my wrongdoing returns us to peace sooner, so be it. However, that does *NOT* include taking ownership of wrongs i have not committed. Doing so is as dishonest as lying. If a situation is misrepresented and blame is accepted accordingly, neither party can actually learn from the outcome, because the lessons as understood are incorrect.
*She seems to have taken the other road, where her happiness is specifically predicated on "Being Right". It really seems as though she's chosen her own need to "Be Right" (and therefore "Happy") over your own happiness. She's asking you to accept that as well.
*looking at how much effort she's putting into this (to be "Right" while still "making it work") is a big red-flag of how desperate she is to maintain control of you. Love is supposed to be about joy, forgiveness, and understanding. Not rules, blame, accusations, and "cited proof of non-abuse".
*Does she make you happy? All other points aside, this is one of the most important. If you really truly feel all the positives outweigh the negatives, i doubt you'd be posting here for advice. Follow your initial instincts.