Code Enforcement Is Harassing Us

Unless they are discriminating for some illegal reason, such as race, code enforcement has pretty much an unfettered right to apply their enforcement efforts as they see fit.  You say other homes have "some of the same" violations as your mother.  If your mother has many violations and the other houses only have some, that is a logical reason to enforce against your mother as a priority.  Code enforcement also tends to follow the "squeaky wheel gets greased" rule, by which I mean they often only enforce where there are complaints.  So if there have been complaints about your mother's house and not others, again that is a logical and legal reason to focus on her.  The last issue is simply being "on the radar."  Once they have a file open on a property, it will get more attention.  Again, there is nothing illegal about that.