Wat is de neukpartij?

I knew the girl was trouble, but it's always nice to allow the extended clan to stay if they need to. She'd always been known as a bit of a wrong'un, but after the first few days we were getting on well and started to bond for the first time.... she'd even let me borrow a book of hers, which was a fun read. It was when I decided to pop into the guest room where she was staying to return the book, that things took a turn for the... erm, interesting, shall we say!?