well is it her first time? that can bring a few different affectations. first timers often experience some nausea or flulike symptoms.
1/2 ounce to a pound of butter sounds a little weak to me but then again i am anything but new at this. did you try them at all?
i just looked up the injection and the most common side effect it shows is flu like symptoms.
no one really knows the interaction between cannabis and well pretty much any other drug or at least there is very little info for it.
Id be inclined to guess it was her injection, i use mj to alleviate the flu on the rare occasions when i get it same with colds. it helps immensely. but i smoke more often or vaporize than anything else.
hopefully there may be someone else who can give you more definitive answers, but i think looking into the injection is a good place to start.