First, what is the result of git branch -a on machine B?
Second, you have already deleted heads/devel on origin, so that’s why you can’t delete it from machine B.
Try
git branch -r -d origin/devel
or
git remote prune origin
or
git fetch origin --prune
and feel free to add --dry-run to the end of your git statement to see the result of running it without actually running it.
Docs for git remote prune and git branch.