I took it personally this time because it was the first time she had done this, and given her previous long-standing frank, clear interest and then for it to just disappear,yeah, it seemed from my perspective, rather dismissive.

This might sound odd given the context, but my anger at her was also driven by fear:

"oh no, she's went and shut down, she's burning bridges because shes imminently suicidal."

I should know: I am a survivor of suicide, and done precisely that. i was angry at her, and scared for her as well. This might be again succumbing to "trying to pin things down too much" but it feels like things are dead in the water now.

In any case, it seems to me that there would never be any certainty or any loyalty on her part. One minute she likes me, the next she is indifferent. This to me, logically, renders all interactions suspect and all declarations of affection counterfeit. The house on sand will crash into the ocean; the one on rock will not.

So no, I will not be pursuing her. You liken her to a butterfly; and but with a mere flap of its wing, it creates a tornado. Put bluntly, she just isn't that special, or valuable.

Her loss.