Luella trespasses on Merchandise Mart's property. Through the use of reasonable force, Merchandise Mart's security guard Norris detains Luella until the police arrive. Merchandise Mart is liable for:

Merchandise Mart is liable for Trespassing on private property.

Explanation:

Luella has clearly trespassed on the private property of Merchandise Mart and the security guard is well within their rights to detain such person in the absence of the police.

So the Merchandise Mart may put up a case for trespassing and civic disturbance during the hours of work, if they can prove that the premises entered are indeed private property and not public access in which case Luella may have a right to defend themselves.