She looked familiar to me in this wonderful film, but it turns out I'd probably never seen her before. She was fabulously funny! And I really loved the film.

Did she remind you a little of Anne Bancroft? Like you, I thought the flashbacks and Arthur where the best bits in it. I found the other two timeframes a bit dreary and the lovers (the illustrator and the actress) very moany! They seemed to look for problems that weren't there. I would have preferred to follow the earliest timeframe.
Now put that gun down Heidi! Youre not solving anything by massacring people!

She (and the dog) are the only reasons to see this exercise in tedium. If you like her, you don't want to miss her in this. It made me want to look out for her in future projects.