Hi Caspian! What a froggy dilema? You will probably get many varied responses to it. Understand how we all feel about frogs; but this lady appears to have made it clear to "bug off," so don't think she wants advice. You have not seen the frog; so she could be actually pulling your leg. Or it might be true and the frog in not being cared for right.
You could contact animal welfare authorities (if available). However; since you haven't seen the abused frog, you are opening yourself to an embarrassment and maybe a lawsuit.
Confiscate the frog? What do you plan to do? Forced "break in and enter" to rescue a frog? That could end up from very bad to total disaster. My advice... walk away from this issue and be nice to your frogs!