From my perspective, go for the fastest available option. If the 850 saves the operator from waiting, then for the extra money, it's worth it. If three or four sets of holders allows to batch line up operations, that is worth it.
Look at the ergonomics of the work space - would a 12x16 light panel help for loading the holders? Make space for, and buy one on the LHS of the station. Would another light panel help for checking the out feed to the neg sleeves? Make space for, and buy one for the RHS of the station. Space for films waiting to be loaded / post loaded. That really helps.
Twin checks on the films/ work orders - no questions about file naming. Saves time and thought. Fast computer running the scanning, with fast drives and plenty of ram. She'll be going between scanning S/W, PS / LR / finder / browser (wetransfer, dropbox, whatever). Any time the operator is waiting for the computer is time lost, is energy lost, is focus lost. The computer doesn't need to be a monster, but going cheap and tapping fingers never leaves you feeling good in a production environment.
Post C19, light panels can be repurposed, the scanner can still be used, and the computer will be current.
In my little production area, I have a 6' desk with my main mac and a coiuple of screens. Behind that is a standing desk with the Noritsu scanner. Desk is only 4' wide - should be 6' or more. My office is too small for what I'm doing. If she is the only connecting link between students' analogue capture and their images, then hopefully the school will make the relatively small expenditure to help her function most efficiently.
A bonus feature would be having dedicated storage for all the film holders, envelopes, and gizmos she might need to work efficiently. A clean compressed air line is a real benefit for making sure the glass and film is clear of dust.