Eulogy is not a requirement
Dear Prudence,
My mother passed away two weeks ago. To those outside our immediate family, she was this sweet, wonderful woman who people thought the world of. Behind closed doors, she was a mercurial tyrant who had everyone walking on eggshells to avoid triggering her wrath, terrorized me, and drove my younger sister to an eating disorder while our father coped with alcohol.
The problem I am facing is twofold: I will be forced to interact with person after person while stewing in silent outrage with a fake smile plastered on my face as they offer condolences for my “loss” and listen to all of the positive things people will be telling me about my mother knowing they are untrue. It has also fallen to me to deliver the eulogy. I have absolutely NO idea how to pull this off—I refuse to invent virtues this woman didn’t have. My dad is not capable of doing it, and my sister would have a panic attack. I am miserable at the prospect of writing a hagiography for my abuser. How do I handle this?
Re: Eulogy is not a requirement
Or if you feel that is not an appropriate solution, cite your feelings as too new to give more than a few words. The father and sister can know you're speaking the truth while the rest will know that you're being coy. DH's grandmother was a hard lady to deal with and words were still said that were positive. If you truly feel it's not possible to deliver anything positive then white lie your way out of it.
And simply say, "Thank you so much for your condolences." Those who were not aware enough of the issues your mother caused don't need to find out about them in her death. If you're having a public event then practice the non-response.