I have just started dabbling with this. Some quick thoughts. Actual dying is about 15 mins or so. Getting the water to near boiling is what takes the longest. 30 max including tidying up assuming you are simply dying one bunch of material with a single bath (i.e. not dying one colour and then rinsing and dying another colour). :-) Drying can take a long time so best to have somewhere to let things dry overnight (or longer in the case of hair). The other thing you have to factor in is cleaning the materials before dying. But this involves just letting materials soak in Venpol or its equivalent, say overnight.

The thing she won't like is the smell...the heated vinegar/dye solution isn't that bad but then it's not roses either.