Hey Rivets -- have you tried swapping mike sources at her end of the line. No amount of signal processing will help you if the source is doing the distorting.
Remember the good `ol days of carbon mikes - that yer had to pound against something for awhile if they had sat unused for too long? Does she use a headset or use a mic internal to the PC, or possibly one internal to the camera? Simple enough to substitute. If multiple mics are present, they might be competing for who's on top and distorting that way.
As technology grows more complicated - meaning that one can no longer see the filaments glowing in most of my pc's - the old way of substituting one ting for another along the critical path is still a consistent winner. May not solve all problems, but sure narrows the discussion.
One approach to substitution is to use another application altogether. I have found Google voice and video chat to be very handy as alternates to Skype in long-path noisy cases possibly like yours. The G app is quick enough to install and, for my world where it's often not acceptable to have online background apps like Skype that want to be perpetually running and frequently updating selves over the network without explicit permission, then Gmail chat is a winner cause it all goes away (operationally speaking) when you terminate the browser link to Gmail.