So she should be forced to abandon a working factory for someone else so use the space? Is your house bigger than you absolutely need? Do you have a garden? Would you like to be forced to give it up so multiple smaller living units could be built?
It is hers, she can choose to maintain it for its current use if she wishes, unless it is causing harm. There is a grey area here with derelict sites, as that is a waste of space and often they can be dangerous, but that does not appear to be the case here.
FWIW it sounds like it's not even a working factory any more.
A rich person has every right to burn a pile of money or spend it on some extravagant luxury, but we still consider it distasteful when they do. Particularly when that pile of money is unearned, which seems to be the case here - it's only an accident of birth, and an accident of factory location, that means the factory is now on such valuable land.
In my ideal world there would be a land value tax so that people paid a fair rate to the rest of society for the land they were taking up, rather than the lottery of buying land once and owning it forever.
Property taxes and land value taxes are absolutely not the same. Unlike property taxes, land value taxes do not cause any deadweight costs, as the supply of land is fixed and can even increase allocational efficiency.
Property taxes require people to pay a portion of the assessed value of property they hold.
Land value tax implies the existence of a third party with no aligned incentive that punishes you for not using your property in the manner they deem most suitable.
This should not have been downvoted (at least the first part of the comment). The commenter before explicitly stated in his ideal world land would be taxed at a fair value instead of people purchasing it and owning forever..
It is hers, she can choose to maintain it for its current use if she wishes, unless it is causing harm. There is a grey area here with derelict sites, as that is a waste of space and often they can be dangerous, but that does not appear to be the case here.