Oh, so sorry to hear this. Wish I'd seen it sooner.
No, you're wrong, this isn't your fault at all. You've still got a lot of guilt going on.
I don't think that you subconsciously handed her the phone because you knew that would spark the end. That doesn't make sense. I don't think you were hiding anything in the text messages that you knew would provoke Alex to leave.
I do think you wanted Alex to end it for you, and that you've wanted that for a long time. But I think you were also trying really hard to make things work with her. You were the one who was being really patient with HER.
My college boyfriend wanted to get me to break up with him--and believe me, he treated me like shit to bring that about. There was no trying, no unconscious sabotage with him.
I think Alex is the one with the subconsciously unhealthy behavior here. Why did she read your texts on a day that you were trying to make special for her? Why did she extrapolate imaginary lies from texts that you weren't even trying to hide from her? Why did she pick a public fight in a way that humiliated you? Why did she say cruel things to you?
She's the one with the problems here.
So please stop beating yourself up.
In a less negative slant, Alex herself, in her own heart, may have known the relationship was over for quite some time, and she was looking for an excuse to end things on her own terms.
Two bits of advice:
1) Things will be okay. It may take a while, but really, trulyou will someday be okay again.
2) Don't throw yourself more into intense feelings for K because of this. Give yourself some personal space to deal with this. Take it slow with K.
Keep us posted.
Single, straight, female, solo, non-monogamous.