Don’t explain the B. It just never comes across well!
Bates has typically deferred lots of kids from ED to RD, so probably the most important thing she can do in that LOCI is add something to her application that wasn’t there before. The update on the capstone is in that category as are any new awatds, etc.
The goal here is to give the AO, who didn’t see her as compelling enough in the ED round, a reason to change that opinion.