we have the same problem in our shop. and we (the developer) end up committing those changes for the designer. what i'm planning to have is a small cgi script that has a textbox for commit message and a button. that script should commit the latest changes of the whole tree. (or modify some svn web frontend to interact with the working copy... hmmmm).
teaching the designer to use that interface would be much easier than teaching her to use ssh
i've tried tortoise svn, but the problem is that the designer need to work with a running version and the webapp runs on linux.