When you compare lamia's bodies to a human's there are a number of differences.

For example...

Having a long, forked tongue.

Lamias, like snakes, posses an organ to detect smells inside their mouth.

In order to bring the scent particles to their mouths, they use an elongated tongue.

That sensory organ is split into two parts...

As is the tongue itself.

Darling! Your ice cream!

Ah...

Oh darn, now my hands are all sticky.

Ehehe, just kidding darling!

I just wanted a taste of your ice cream.

Among the residual snake-like traits lamias have, they keep their elongated tongue...

Oh, that smells good! What are they selling?

Uh Miia, your tongue is sticking out a bit...

...As well as exposing their tongue as a response to tasty smells.