I'm so very sorry that you've lost your mum.
If it helps, my Will states a direct cremation with no funeral. I've written that if people want to throw a party and celebrate the fact I've buggered off (insensitive of me at this time, I know, but your mum may have been thinking along the same way as me), then party, have fun.
But, imo, I don't want the expense and the lamenting and drama of a funeral. I don't want people mourning me. I want people's last memories of me to be bossing nurses in hospital for chocolate or water that doesn't taste like dust. To be the one who everyone rolls their eyes at when my name is mentioned and laughing.
Maybe this is what your mum wanted? To be remembered for being herself. Not a coffin. But your mum who loved every single ounce of you, who doesn't want to cause more grief, who wants you to know how much you meant to her, even if you thought you didn't, you did. She's given you this and she's done it with love. She's tried to spare you from hurting, that's your mum, always putting you first.