Can you provide the say "protocole" they gave to the player? Do you have proof of what you're saying? If this part of the facility was indeed closed, they should lock it. Plain and simple, if they don't they are in risk of accident happening, that is called negligence. It's the same as if someone is getting hit on the head on a construction site, a pedestrian is not supposed to be there, but if they had access to the site without breaking in and something happen, they are responsible, not the victim.
The rest of your analysis is pretty dumb, the USTA makes tons of money, they can afford lawyers way more expensive than Genie. There's speculation for $1.6M which is way more than a lawsuit would cost. Allistair has nothing to do with this since the USOpen is ruled by the ITF, since the big tournament in the US are very profitable for Stacy, she'd be dumb to put pressure on the USTA to give a player some money, and that even if it was Sharapova or Serena. If they want to settle it's because they feel that they are in hot water.