I have no idea if Matisse even had children. So, to be plain, this a work of fiction and Marge Matisse bears no relation to any of Matisse's surviving relatives. Marge does not exist, more's the pity. She'd be a great dinner party guest, full of spurious stories about the old man, whom she never really met. She'd leave thick lipstick on your cups and not allow anyone else to talk and need helping home, declaring "I only had one glass of wine!"
The main problem is, despite all my efforts, she persists in looking like one of Matisse's paintings. This means if she came to dinner, it would be like entertaining a particularly elegant toon.