Betty Freeman, who died at her home in Los Angeles on Sunday, was a leading patron of the arts and new music. That's her in David Hockney's Beverly Hills Housewife, per Tyler Green on Facebook. From photographer Brent Phelps:

She was the force behind such modern classics as John Adam’s opera Nixon in China, Steve Reich’s electronic string quartet Different Trains and Harrison Birtwistle’s Antiphonies, and the dedicatee of works by Cage, Feldman, Berio and dozens more. She found Harry Partch living on the streets of Los Angeles and gave him shelter in her garage. In all, more than 80 composers were beneficiaries of her support, in over 400 works. Betty was also a close friend of the artists David Hockney and R B Kitaj and a gifted photographer in her own right. Her portraits of modern composers, taken with the privilege of close and prolonged collaboration, are exclusively represented by Lebrecht Music and Arts Photo Library.

An accomplished pianist, Betty established a musical salon in Los Angeles in the 1980s. She had no nostalgia for 19th century romantics and supported without prejudice both streams of post-modernism - both the minimalist and atonal tendencies. Few people could claim to be a close friend of both Philip Glass and Pierre Boulez.

The Online Archive of California page on Freeman's papers at UC San Diego says:

Freeman began her activities as a philanthropist and supporter of musicians in 1961 by contributing to a young musician's legal defense. Since then, she has assisted more than 30 contemporary composers. Beginning in 1964, Freeman has served on the board of "Encounters," the Pasadena Art Museum's concert program, and beginning in 1981, she hosted her Monday Evening Musicales, a venue for the new works of composers, in her Beverly Hills home. She is currently on the board of the Los Angeles Philharmonic, having supported for over a decade the orchestra's New Music Group until its close in 1991.

Here's a Wikipedia page on Freeman.

Edited with new info