Wow, Andrew, no wonder you are concerned. She needs vetting. Can you speak
to this neighbor, simply saying that you were happy to see her at the window
as you had missed seeing her, but noticed some terrible sores and are
wondering what they are? This might move this cretin to take care of her.

If not, are there any animal welfare leagues or humane societies you could
contact after you have made an effort to contact the neighbor? This is
terrible. However, you ought to contact the neighbor first as perhaps she is
under treatment? Not likely, I know.

-> http://members.lycos.co.uk/waweldragon5/html0006/page1.htm   is the correct
-> link

Do you live somewhere where there is an SPCA, or humane society,
or some other offical organization that concerns itself with the
welfare of animals? If so, give them a call and tell them you
know of a cat that may need medical attention. They will keep
your name out of it, but from what you say, the neighbor will
probably think it was you.

If you don't know if any of these places exist in your area, call
the police department non-emergency number and ask.

If you only have animal control in your area, call them and see if
they will do anything.

Please keep us posted.