I don't deal well with people that are travel agents for guilt trips and their bad boundaries. You aren't hurting her, she's choosing to disrespect your decisions and to be hurt by setting expectations based on her values. That's her problem, not yours. I would feel worse stringing her along, giving her some false hope.
Hey mom, I'll attend the Memorial. It's like what, a couple hours of my life. Then you can sit down and go through Crisis of Conscience with me for a few hours. What? You don't want to? Oh, this only works one way in our relationship? Well then, I guess I won't be going, eh.