She made an appearance at Biola University some years back, and the appearance was protested against by some of the students, who contended that she was, at best, a "new-age" writer and not a Christian.
The administration overrode the protest and she appeared anyway.
Her obituary in this morning's Los Angeles Times states that she considered herself to be a "light Episcopalian." Since Episcopalians are already pretty light, I guess that tells us where she was at, religiously...
Not to get into a big argument, but I actually really liked her book Walking on Water as reflections of a Christian artist, was very conservative on many points, and would recommend it with the caviat that, like many Anglicans, she's too accepting of Catholicism.