I think the mermaid personality is more likely lighthearted and carefree. Fantasy novels and movies generally represent intelligent nonhumans, such as space aliens or fairies or mermaids, as morally superior to us, living in peace and harmony humans can only envy. This trend has changed in recent years with cynical, realistic naturalism becoming the dominant literary style, but the preconception lingers that mermaids or otherworldly creatures live in a Utopia. Elaine Morgan points out that aquatic mammals seem to be very playful, intelligent and gentle animals. The playful nature of dolphins is common knowledge, as is their kind habit of helping drowning humans back to land.
Otters are more intelligent and fun-loving than their close land relatives.
Sirenia are docile creatures who rarely fight even when attacked. If the principle holds true, mermaids may be as peaceful and happy as popular fantasy would have them. The Tale of the Mermaid and Her Kin. The Citadel Press, New York City. Copyright 1957 by R. Carrington.