Anyone had success eliminating stick fleas?

I know an old woman I take care of who lives on a free-range farm with 3 senior cats, the livestock became infected and the infection spreads to all the animals.

I get at least a dozen stick fleas off the animals daily. I remove them, but it's not enough. The infestation is so bad, it feels hopeless and she fights with me any time I try to offer solutions and stone walls me.

She refuses to take them to a vet. I can forcefully take them and pay for it myself, but I don't know how helpful that will actually be since it's pointless to treat the pets without treating the environment. If there's meds that will help, I will look into them. I would look into rehoming them but there's simply nowhere for them to go.

Anyone who has any idea, I'm all ears. I've exhausted nearly everything I can think of.

TL;DR: Seeking help to remedy a stick-flea household infestation.