I don't have much to add, other than that when LSAT is testing us on the same word/term being used two different ways, we should not pick it unless we have the ability to do what the previous poster did: provide two different definitions/usages of the word.
I think the test-writers were trying to make Mary's vested interest in this topic slightly less obvious by using "outdoor advertising company" rather than "billboard company".
If Baysville takes away Mary's billboards, she'll have to funnel all her outdoor advertising efforts into sky-writers and sponsored blimps.