I'm not sure how similar these angels are, but I have a coral beauty that just LOVES the Formula 2 flake, flake (nutritionally enhanced) brine shrimp, and frozen prime reef as a treat. Maybe there's something to be said about giving your angel some variety...oh, by the way, my clowns enjoy all of these things too, plus the meat that I feed my brittles and coral banded shrimp.
Just keep trying different foods, I'm sure you'll hit on one that she can't resist, then BOOM...everything looks great!!
I have tried to give my angel algea on a clip (the brown stuff), but she really hasn't shown any interest in it, so I gave up on it. Your's might be different though, give it a try!!
Beautiful fish, by the way. Best of luck with her.
Lisa :happyfish