I got my regal about three or so months ago. When I first got her she would not eat anything. So I feed clams. She devoured them. After a week I would remove the meat from the shell. Then I would press my homemade mush into it. It tricked her, she ate it perfectly. After that she will eat ANYTHING. She now will eat any food I have from my hand. As for keeping them with other angels, it can be done. Just be 100% sure your regal is perfectly acclimated to life in a glass box. Then add another angel. I would reccomend one of the more docile angels. I now have a potters, flame, and Majestic with my regal. they all get along great. Just go slow with the regal and be sure she is comfortable.
~Michael