I went to www.google.com and found some info that may help you, but nothing specific:
Society of Children's Book Writers and Illustrators (Los Angeles, CA) general questions:firstname.lastname@example.org
I believe they may help you find some information.
Also try borrowing any of her books from your local library through inter-library loan - there may be a biography of the illustrator in one of them...but I find that there usually is NOT...unfortunately.
Probably a good source of info would be the Writers and Illustrators' Society above as they could point you in the right direction.