The recurring character Ariande Oliver (present in a number of Agatha Christie's novels) seems to be at least partially self-insertion by Christie (At the very least, both write mystery fiction stories featuring a foreign detective). Besides this superficial resemblance, how much does she actually resemble Christie herself?
This article suggests that Oliver was an exaggeration of herself. I expect she had fun doing that!
Ariadne Oliver is a successful detective novelist that appears in two short stories (with Parker Pyne in Parker Pyne Investigates) and seven novels (six of them with Hercule Poirot). The middle-aged writer of detective stories is broad-shouldered and has "rebellious" gray hair, sometimes accentuated with hair extensions. Ariadne Oliver is known for her love for apples and her strong belief in woman's intuition. She is also the creator of the Finnish detective Sven Hjerson, of whom she has a great dislike. The character of Mrs. Oliver is an exaggerated version of Agatha Christie herself (Agatha has shown dislike towards Poirot, her creation, and Agatha was known for eating apples, too).
That doesn't answer your question to what extent the character actually resembles Christie, but it does vindicate your theory. It could be interesting to assess a biography of Christie against the character. (It may well have been done already, but I haven't found it. Yet.)