"She calls for help to the public."
Translation:Elle lance un appel au public.
No, that does not work. As an alternative, you could say "elle appelle le public à l'aide".
I like your alternative to the 'lance', which I generally refer to 'throw', like 'jeter' ! Thank you.
I used "à l'aide" but I was seriously thinking of using "au secours" as well. I've heard both many times.
"au secours" is really strong, when something horrible happens. Appeler à l'aide can be a financial help or just a favour.
Elle appelle à l'aide au public, ou, elle appelle à l'aide du public. Would either of these work? I think part of the problem is the sentence in English. It should be "she calls to the public for help" or "she calls for help from the public."
"Elle appelle le public à l'aide" would be a good alternative. Literally meaning that she calls the public to get help (I know that is not good English, just for you to get the basic structure).