Basically the English club is an “easy A” that pads their grades and by electing to not take that part of the class the student will be held to a somewhat higher standard?

How about this:

Calculate her grade based on 85 points.

Also calculate the class average based on 85 points as well as 100 points.

Give her the difference it makes in the class average.

Example:

Her: A=53, B=12, C=8

Class Average: A=55 B=12 C=9 D=15

Student X: A=57 B=13 C=10 D=15

Student Y: A=49 B=11 C=5 D=15

The class average would be 91, but would only be an 89 without the “fun” section. On average the class would get just 2 points by attending the easy part.

Student X’s average would be 95, but would only have been a 94 without the fun part.

Student Y’s average would be 80, but would only have been a 76 without the fun part.

Her average would be an 86, but she gets a two point adjustment to her average to compensate for the easy section she isn’t taking, leaving her with an 88.