Delphinium Potter: the Inland Taipan

In environments with little magic Lamia genes go dormant. If a Lamia's child is born a squib they will appear entirely human, development of the fetus in a non-magical environment can also result in a magic-less and entirely human child.
Coincidentally Lily Evans father is one of these children, like most Lamia squibs he was hidden with Muggles for his own protection(Lamia society is quite brutal after all).
Lily Evans is conceived, born, and raised in an entirely muggle environment. She has a Lamia's easy control over their magic and a resistance to deadly poisons but nothing else really.
Her daughter Delphinium on the other hand... well let's just say the Lamia blood is strong in her.