Yes. It's an insulting word. Means scumbag / scum.

Different words equivalent function. 人渣 [rén zhā] scumbag As you can see in the word "zhā", there is a "ā" ( /ɑː/ ) sound, which means your mouth will open widely to pronounce hence very strong. When someone get totally piss off, they will call others “人渣！”.

渣 can mean scum, slag; something in which all vitality is drained away. For example, overcooked bacon with every single drop of oil gone (not crispy) or a piece of sugarcane in which all its juices are extracted, what is leftover is then called 渣. Whoever did the translation for the Standard & Chartered Bank (渣打银行) is a joke on the British blokes who do not know Chinese. Though a insult but does not carry the same harshness as "a *>#$%! piece of >$%!" This would translate as 狗屎不如, (even dog shit is better). Due to cultural biases, sometimes direct translation does not convey the same degree of severity in the target language. Here's an interesting article for you... http://www.yoyochinese.com/blog/Chinese-Insults-How-Name-Call-Pro-Part-1

I can image the girl is so angry.

Yes it's considerded as a swearing.Like "Scum" in English.