That was poly done very poorly. She didn't even tell you about the other guy from the get go. Ideally, you two would also have had a more stable relationship (i.e. Longer than two months of dating) before she even thought about bringing someone else in.
There is a good saying for poly relationships: "Go at the pace of the one struggling the most." Doesn't sound to me like this was even considered by her.
You read, tried to work things out, asked for open and honest communication, and wanted to know your metamour. Sounds like you were doing everything you could.
ETA: I get huge warning bells when I hear about a "poly" person telling a partner that they're the favourite. You have to wonder what she's saying to the other guy, whom she presumably also cares for.
I'm a pansexual female, married to and living with Indigo
(straight male), in a relationship with and living with Mr. A (straight, mono male).
One day I might stop "practicing" polyamory and just start living it!
Here Be Dragons
Originally Posted by AutumnalTone
Nobody gets a toaster oven for recruiting monos.