The drawback: While they can't raise her rent above the percentages K.M. outlined, they can't kick her out and they can't refuse to lawfully maintain a habitable apartment with functioning plumbing, heating and ventilation, they don't have to do upgrades. Most of the units there have had some significant remodeling and modernization.
A friend of mine from high school lives in the LA area and has a rent controlled apartment. He seems to have to fight an eviction every year. Granted, I only hear his side of the story that he posts on Facebook, but he said they'll scrounge for just about any legal reason to kick a rent controlled person out. Sounds like your wife's sorority sister has a better landlord than he does.
I realize living in a Midwestern college town can be boring and has its own stressors, but I love owning my own 2,000 square foot house with a reasonable mortgage for my roughly $80,000/yr salary. (Obviously, I got out of radio a long time ago!) Although any problem is now mine (and I had to write a $13,000 check last month after my A/C went out), I don't miss renting and never want to go back to that. And, no, I wouldn't give up my $80,000/yr job here for a $90,000/yr radio job in LA.