You should never house dragons together. They are solitary animals and do not benefit from being housed in numbers. One could end up becoming very stressed and stop eating due to being bullied, and she could possibly end up injured or killed. I know this from experience, I have a dragon with a nubby tail because I was naive and had them together. Even if the dragons seem like best friends, they could turn in an instant. You need to buy another enclosure in order to get another dragon. It will be more costly to buy a whole new enclosure, but it will save your dragon's life.