Why should he not? She was his assistant.
In 1937 Lydia Delectorskaya posed for Matisse in a purple robe. At the time Matisse had no intention to paint a portrait that looked like a photograph. When accused of painting unrealistic images of women Matisse explained, "I do not create a woman, I make a picture." He readily admitted that his images were not faithful re-creations of reality. * http://www.mystudios.com/art/modern/matisse/matisse-purple-robes.html
did matisse paint with only oils
To paint pictures.
In Paris.
Not until he died in 1954.
It was painted in 1911.
long paint brush
Sometimes oil paint sometimes gouache.
Derain was a trusted colleague of Matisse, who also painted a portrait of Matisse. Why should they not?
Gouache
In 1921.
Think it was 1932