It looks like other commenters mostly have it covered but there are definitely a couple options to consider.
1) letting her out of her lease early: Is she paying market rent? or will it rent for significantly more once she is gone and repairs are made? Rentals do definitely slow down in the winter but if you are in a desirable area with a high demand you may be able to fill it quick. Do you plan to do more repair projects? if you have to pay to rent her an office every time she needs repairs this could be a lot of hoops to jump through as oppose to just letting her move out and fixing everything while the unit is vacant.
2) Paying the full cost of a workspace: Assuming the cost is $400 total, will that be worth the trouble to just satisfy her request, get in and get your repairs done without potential trouble from the tenant or with the contractors. If there are unforeseen delays and the tenant is already upset with you then they will be more difficult to work with down the line and while you are already trying to manage your current project. This also goes to my point above about if you plan to do more repairs in the future, the $400 to make her happy now may be worth it to protect you from potential empty months of no rent or headaches with trying to coordinate future maintenance and repairs with a frustrated tenant. It also may set a precedence, she may assume she will get a remote workspace every time any maintenance is taking place so I would also be sure to state that this is because this will take nearly half the month to complete and this will not be a "every time you put in maintenance requests" sort of thing.
Good luck with your project and your tenant!
