Reading the 'Smoking Weed' thread Ashez mentioned a link between hash and asthma, I have never heard this so I did a little research to find out more. whilst doing so I came across this:
http://www.ananova.com/news/story/sm_815965.html?menu=

I agree with being let off the pot but pills and amphs?
seems like an illogical decision to me. Any thoughts?

Yeah, bit suspicious.

Pills can help parkinsons sufferes who use el-dopa and can't control the steadyness of their movement, I saw a sufferer on a Horizon documentary who could hardly stand up, when he swallowed a pill, he was filmed in the Gym doing somersaults, forward rolls and other activities that would have been impossible had it not been for the combination of the prescribed el-dopa and MDMA.

I think it basically goes with the territory, if you have to buy illegal drugs to ease a condition, it's difficult to draw a line between them.

Having taken all three at the same time, I reckon she maybe used the Amph and pill just so she wasn't walking about stoned all the time. The effects of all three don't cancel each other out, but if you are smoking cannabis to aid an illness, you aren't doing your social life any good, maybe she just wanted a good night out.