I had this about 7 years ago and its a horrible illness..
You will get people telling you that the glands in your neck swell which is rubbish..
What it does do is attack all the glands in your body from top to bottom, so she will gets aches and pains everywhere..
She will get flu type syptoms ( shivers and shakes ) headaches,sickness, loss of appitite, the full works..
With me it gradually got worse after 3 weeks and in the mornings i could hardly walk because of the aches in my legs..
I could not face any proper food, all i ate was sweet stuff like puddings and cakes.. ( i lived on cheesecake for about 4 weeks )
She will probabily be off work for a minimum of 4 or 5 weeks probabily longer..
If all that wasnt enough, the recovery is the most important part because if you rush yourself back to work it can develop into Chronic Fatique Syndrome ..
( words from my GP )
Even now 7 years on i still suffer from the effects of it..
She will feel really poorly ay times mate so look after her, try and get her to drink fruit juice and eat. If she wont eat they is not much you can do as you just cant face food so try sweet stuff.
All the best..