Mary buys cookies made with SugarFree ,an artificial sweetener , which tastes as sweet as the corn syrup that her brother loves but where there are fewer calories than in an equivalent amount of corn syrup .
The answer is :
Mary buys cookies made with sugarFree, an artificial sweetener ,which tastes as sweet as corn syrup that her brother loves but which contains fewer calories than does as equivalent amount of corn syrup .
I am confused about this answer . Here we have two back to back modifiers .First one being "an artificial sweetener" and the second one being "which tastes as sweet...." . Is is not incorrect to use back to back modifiers ?