There are instructions on the side but you should know that should should lie her down and call an ambulance if you need to use it.
Pull off the grey cap, push the BLACK end hard into the outside of her thigh and press hard, hold for 10 secs. Its actually quite hard to activate, you need to press hard. If you can’t get a trainer pen you can ask that she gives you her old pens when they expire so you can have a go on something like an orange.
If she is that allergic you would be most helpful by suggesting that you have a nut free office. you might get nuts on the door handles or in the air con.
Most importantly, do not get it the wrong way round. In their excitement keeno first aiders have managed to inject their own thumbs, which if not treated can make your thumb fall off. 😮