Answer to 1) I agree with redpepper. Why is it such a big deal that she used text messaging? Not everyone is good at vocalizing. I trip all over my words when I try to say thing orally, and sometimes end up phrasing things poorly, in a way that hurts someone's feelings but wasn't at all what I intended. Then it seems like I'm back peddling or lying or changing my story, when really I'm just trying to phrase it the way it is in my head.
I'm an INTJ. That means I can't always put my thoughts into words. For me, writing them down, editing, re-editing, and re-re-editing helps me get them in the form that most closely matches what I'm thinking. At that point, it's easier to give the written copy to the person than read it out loud or something.
She was probably scared to death to tell you. It's a big bomb to drop, and I'm guessing text message was the only way she could get up the courage to do it. It's better than not telling you at all...
Answer to 2) I told my now-husband the day we got involved. He had spent the night (cuddling) and by morning it was obvious that it was something special. I've always known I was poly, and it was very important to me that he know that, so I told him outright. It helped that I was in another semi-relationship, and so I knew I didn't want to just drop that guy to be with my now-husband.
But that's also something of a luxury by a lot of standards. Not everyone is born knowing that monogamy is never going to cut it for them. It took me years to learn there's actually a word for it.
Now what I think about the rest of it. First of all, this alpha stuff sounds possessive. Some girls think it's sexy when their boyfriends get jealous, like it's supposed to mean they care or some crap. I think it comes across more like "I think you're my property, and I'm going to decide what my property is allowed to do."
You don't sound supportive of poly at all. That's perfectly fine and acceptable. If you don't like the idea of poly, then just come out and say so, don't pussy foot around it and pretend to be something you're not. That's lying to yourself and to everyone involved with you.
I also don't like her motives for encouraging you to be with someone else. If she wants to have other boyfriends, that should be the focus of her discussions. She'd might as well say she wants you to get a tattoo so that she can get one. It makes no sense.
Labels are sticky and I hate the glue they leave behind.