particles - Why is が added at the end of この小娘が in this clip?

Audio Clip

Is something being omitted here? Is it just a figure of speech?

Answer

Nothing is omitted there.

This 「が」 is a sentence-ending particle expressing an insult, swearing, cussing, etc.

It is very often pronounced 「がっ」 by us native speakers.

「この小娘{こむすめ}が（っ）！」

Thus means:

"You little slip of a girl!" or

"You little bi***!"

The "right" translation will always depend on the context.

The suffix of insult 「め」 is often inserted between the noun and the 「が（っ）」 (but not in that clip).