There is no evidence that Miss Emily actually saw the men or knew what they doing if she did see them. Faulkner tells us "So the next night, after midnight, four men crossed Miss Emily's lawn and slunk about the house like burglars" and then "As they recrossed the lawn, a window that had been dark was lighted and Miss Emily sat in it, the light behind her, and her upright torso motionless as that of an idol."
Does an idol see its worshippers? No. Do we know which way Miss Emily is looking? Not for sure. We also don't know if she was paying attention, or if the men succeeded in acting like thieves. As a result, we simply can't know.
If she did see them, we might suggest she took their service as her due, as an idol or Southern lady does.