one problem may be that you do work to manipulate brfss2013 , but don't assign the result to any name so it is not available for future steps. I would guess mean_dv is therefore not there. but I would expect you to have a different error than the one shown.
The error shown might simply be a namespace confusion.
do
getAnywhere(aes)
This should show where aes is coming from which should be only
A single object matching ‘aes’ was found
It was found in the following places
package:ggplot2
namespace:ggplot2
if you have other things in there, thats your problem.
restart your rsession and load only the tidyverse and try again.