1. To be able to claim home office expenses, her employer will need to fill out Form T2200.
2. Complete on her return the T777 - Statement of Employment Expenses form.
For more info: http://www.cra-arc.gc.ca/tx/ndvdls/tpcs/ncm-tx/rtrn/cmpltng/ddctns/lns206-236/229/cmmssn/hm-eng.html