Complex sentence: Ozma herself will check in with Dorothy from time-to-time, to make sure that she is all right, and promising that if Dorothy ever wishes to return to Oz, she will make it so.
Split into simpler sentences: Ozma herself will check in with Dorothy from time-to-time to make sure that she is all right. Ozma also promises that if Dorothy ever wishes to return to Oz, she will make it so.