A HUNDRED dollars a month-it's a fortune " Jean Bruce exclaimed gayly, pirouetting about on her tip-toes in front of a huge Japanese umbrella fastened upright in the ground in the middle of the orchard at the Rainbow Ranch. Jacqueline Ralston gazed half convinced at the sheet of paper she held in her hand. She was sitting in Turkish fashion on the grass just outside the umbrella and, as her Mexican hat had been flung aside, the spring sun shone directly down on the bright bronze of her hair and warmed to a richer rose the brilliant color in her cheeks. The past few months had wrought little change in her, save that the lifting of the clouds from about her home had left her more radiant and full of purpose than ever before.