Contractor Among Contractors
I have clients who have husband and wife contracting in the same company and it works OK. I'm not sure it would in your case if the contract is only four months long, as you'd need to muck about with the shareholding more than I'd be comfortable with. TBH, I'm not sure I'd even bother with a limited company at all for that length of time. Consider umbrella.
If your wife does decide to form a company, remember that whatever accounting she's done in the past, these will probably not be transferrable skills for the requirements of a contracting company. As has been alluded to, contractor "accounting" is really specific tax expertise rather than double entry book-keeping. And, given that you were of the opinion that IR35 applied only to the IT industry, this would confirm you are in need of such expertise.