Invest in Angelfishes by Helmut Debelius and others. You can get the book from ocean aquatics.

There are many reef safe angelfishes. There are two pieces of advice.
1. Buy healthy juveniles only.
2. Feed them.

Your new angelfish likes fresh mussels so clams are out. Buy her a mussel and it might help her get used to your tank. Good Luck but if you have problems you can always send her my way

Wayne