Honestly, it's tough to say. Most people have a hard time correctly identifying what a "pit bull" is anyway. And when mixed with other breeds it's almost impossible to say for sure.http://www.pbrc.net/poppysplace/games/AdultFindabull/findpitbull_v4.html
However, rental properties with banned breeds don't need to prove anything. They just have to think your dog looks a certain way to make their case. If you're uncertain, I wouldn't risk it. Unless you can get something official in writing
from the landlord saying that this specific dog has permission to live there and is not considered to be of a banned breed... you're taking a risk that won't be fair to her.
Plus, if she's already listed as a Pit Mix somewhere (is she at a shelter or rescue?) then all it would take was a web search for the landlord or a nosy neighbor to bust you. I hate places with breed bans but the only way to fight them is through changing minds with consistent positive PR for the breed. Trying to sneak around the rules only backfires in the end.
She is gorgeous though!