I have psoriasis and get a very occasional small spot of it on my hand, mainly just as we come into winter. I use the CND Lamp with no problem at all.
UV light is a treatment for psoriasis- Id like to put my whole body under the lamp!!
Obviously everyone is different medically but I wouldn't think there would be any problem.
if she has open wounds from the psoriasis on her hands you shouldnt be performing any treatments on her until they have healed. This is what i was taught if there arent any open wounds she will be fine.