An orange survival bag is cheap and effective, they make a good rucksack liner, a) because they're waterproof and b) because the light colour makes it easy to find stuff in your sack. There's no reason to ever be without one! Many people use these orange sacks by entering feet first , they're far more effective if you enter them head first and bring the bag down to your legs. If condensation builds up poke a small hole in the corner. Survival blankets weigh very little so it's worth carrying one but in any sort of wind they're a real nuisance.
Also, a real passion of mine, take some time to give your girlfriend some mapreading and navigation instruction, get her to navigate for the group. It's a great way to build confidence and she's far less likely to get separated.
I agree with what others have said, everyone should have their own gear, including map and compass with the ability to use them.
Bothy bags are great and obviously recommended, but properly used an orange sack works well. I definitely wouldn't use a candle in one though and a small hole poked in the top generally doesn't develop into a tear, unlike survival blankets which shred easily, they're better used stuffed between clothing layers.