if her main office already has AC ( i'm guessing furnace & outside AC unit ) & shes adding a mini split to the main part of the grow ...... why would she get heat build up ????
you have to remember , that was a manufacturing facility at one time & whats there now kept them in cool enough conditions to be able to work . shes just adding extra to combat what the extra lights & dehueys heat would add to it .
I mentioned it because cooling the entire building could get expensive to do. Plus she is having a hard time getting the minisplit. Running something she can get at the local lumber yard and she can install herself might be quicker and surly would be cheaper. Not to mention she would not have to have someone over to vacuum the lines.
She is somewhat smart and the choice will be hers to make. Just giving her a different idea for her to think about.