HELP, my neighbor's dog keeps going potty on my apt doorstep & they just leave it!!!?

Well you could go confront her but that probably won't change anything because she already knows you know she leaves it there and she obvisily doesn't care! Honestly, this seems a little childish but if she can't do a mature thing and pick up after her own dog then pick it up yourself and put it at her front doorstep. See how she feels.lol. Be consistent too maybe she'll get the hint that your not going to put up it.