The nouns »die Schlampe« and »der Schlamper« are nominalizations of the adjective »schlampig« which means »sloppy, slovenly, frowsy, slipshod, blowzy, negligent, ...«.
This adjective can be used to describe actions and results of actions that were not performed with care:
Seine Kleidung lag schlampig auf dem Bett.
His clothes were sloppy on the bed.
Dieses Bild ist nur eine schlampige Skizze.
This picture is just a sloppy sketch.
Children also know this phrase:
Dein Zimmer sieht schlampig aus. Räume es auf!
Your room looks sloppy. Clean it up!
But more often it is used as an attribute for a person that makes a neglige impression, or for a person who performs in a slovenly manner:
Ich kann einen so schlampigen Menschen wie Karl doch nicht als Kellner in einem gehobenen Restaurant wie unserem gebrauchen.
I can't need someone as sloppy as Karl as a waiter in an upscale restaurant like ours.
And so, a male »Schlamper« and a female »Schlampe« in their original meaning are just sloppy persons.
But sloppy women are also believed to not choose their mating partners as careful as other women. So, people believe that it is easy to seduce sloppy women to sex. And this is how the female nominalized form »die Schlampe« got a very strong sexual connotation. English translations that also carry this meaning are »slut, bitch« and many others.
But although this word is a swearword, it has been used so frequent to name any young woman that has fun going to parties, that the women themselves begun to use this term to name themselves. This is an act of female emancipation. Those young woman also want to have the right to have fun, like it was granted to men for centuries. And so they proudly and self-confident use a word to name themselves that was given to them to insult them. And so, they wash off that insulting meaning from that word. In this context it has more the meaning of »party girl«. It still has a sexual connotation, but it is very weak. The dominant connotation is »having fun«.
Something similar did happen to the word »schwul« that first was used to insult male homosexuals. Today »schwul« is the preferred word used by gay people to name themselves.
But parties are not always fun, and this is what the song is about. It is a song about the morning after. It is the story of a girl waking up the next morning, crying about her wounded soul. She wants an arm that catches her and holds her tight.