Some points were brought to my attention in PM and I just want to clarify myself a little now that my anger has subsided.
What I saw in your post was one short sentence about "coming out" and "after days of fighting and crying we came to an agreement" followed by a huge paragraph about how poorly she handled the situation that she was forced into.
I really felt that you were taking no responsibility in the situation and putting all the blame on her reaction.
It upsets me greatly when people use polyamory as a shield for being allowed to cheat. A few days is hardly enough time for a monogamous person to come around to the idea, especially when you're still seeing the other person the whole time. And it outright angers me when cheaters expect polys to support their dishonesty and betrayal.
I do admit that I came off a little too harshly, but what you did to that girl is flat-out cruel. So for you to come here acting like it was all her fault, really rubs me the wrong way.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker