It should be alright! Jade is so confident, he probably has a 95% success rate at convincing people to at least give something a chance... and while I give Frieda a 25% chance of getting triggered into a demented rant over the historical parallels with her own world, Jade would most likely be able to turn that into an advantage ("Please excuse her, it's the PTSD from her own war experiences... you wouldn't want this to happen to your children!"), reducing the overall failure risk for both of them to about 5%.

But depending on how open- or closed-minded the merfolk are, their own variables may apply!