adf biting betta?

[pandora's lily]

a couple days ago i watched my adf "stalk" my betta who was just hanging out on the bottom of my tank and all of a sudden she lunged and hung on to the end of my bettas tail till she was shaken off. scared the crap out of my betta though no harm done fortunately.
i thought she might be hungry enough to try for my betta, but she's getting fed enough for two frogs, maybe she mistook my betta's tail for the shrimp she usually gets (the edges of his tail are white), i dunno, anyone with any suggestions?

also my other frog died about a week ago (i suspect the tank clearer that i put in) and as i only had two now my female is alone, should i get another for her? i know they're social creatures...