a) If she won't let you be there for her, there's nothing you can do about it. It sucks, but it's on her if she keeps pushing you away.
b) This is a big red flag for me in a long-term, committed partnership. I know some people need their space to work through things before they talk about them, but she's treating you like a yo-yo and trying to guilt trip you to boot. She needs to put her big-girl pants on and start communicating like an adult.
c) Don't engage. Walk away. I'm not saying walk away from the relationship, but walk away from the conversation. Tell her clearly, "I'll talk with you when you can be rational and not blame me for your actions and choices, but not before." She chose to lie to you, she chose to break up, she chose not to try to address the growing rift over the past year. NONE of this is your fault and it's not good for you to sit there trying to comfort her while she's heaping abuse on your head. If she can't or won't accept the comfort you're trying to give her, she's going to have to get through this on her own. Being in a relationship is no reason for being someone's whipping boy.
d) Same as c.
Pan Female, Hinge in a V between my mono (straight) husband, Monochrome and my poly (pan) partner, ThatGuyInBlack