In the past, I would be quick to ignore that behavior or just exit the relationship out of frustration.
If in the past you would ignore or exit, then she is understandably not keen on doing emotional work "up front and straight up" with you. Hence her skittering about. Perhaps you need to state to her that your ways have changed and you are more willing to face a thing up front and straight up now.
I think you instinct for a talk is right one and you basically already wrote it. Distilled it is something like this:
"Abby, can we talk? I've noticed you suddenly telling me about other guys that you find attractive and making plans with others. Which is fine since we agree to be open and you know I see other people. But it's so sudden and dramatic in the way you communicate this news to me. This concerns me when coupled with you saying you don't feel important anymore.
Presented that way it feels like you do not tell me the news in a way that is just sharing news and keeping me in the loop that you are dating others now.
Presented that way leaves me feeling like I am being attacked, punished or resented or something. Do you mean it this way -- as an attack? A punishment? Resentment of me somehow? Am I misreading this?
I don't want to break up, I DO think you are very important to me.
What wants or needs do you have that I am not meeting? Will you tell me what those are? How can I be more supportive and nurturing of you?
Will you talk to me more clearly about it all?"
Speak your truth to your partner. Honestly, truthfully, and hopefully they are willing to engage with you in kind so you sort this thing out. Whatever the next phase of this relationship will be.