Dont do it

Late starts, PMT, constant whinging, muscle problems and us women dont like to see that in a man - LOL
I dont help as much as I used to Pj but its the only way we found to keep reliable staff and maintain our standards.
I am still yet to find a trolley that holds enough water and can be easily moved around. Backpacks were too heavy for me to carry when full and did not last long enough to use on a trolley (sorry Tosh !!!). I do commercial bottoms only.
Tax wise, unless she works for free or is a partner (in which case she will be taxed anyway) you will have to set up a PAYE system for her as an employee so no real tax benefits.
Dont forget you will have to have Employees Insurance irrespective of who she is.
I suggest her going self employed. Pay her own Tax and NI and get her own PL insurance.
Good luck Pj's wife, I dont envy you having to put up with Pjs awfull jokes all day.

Sarah