Weigh her. If she is gaining weight too fast, then cut her back to 14 days. If you aren't breeding her, I would go with 14 days. If you are, then go with 10 days, and monitor weight.
If you can see skin between her scales, she is overweight--put her on small rats for a while, 14 days, until she's back to normal, then switch back to the large rats.
Not all ball pythons are alike, you will have to use weight and your eyes to determine when you have a correct feeding schedule worked out.