Who is Kelly from Trainspotting and what is their importance?

Kelly is a friend of Alison and meets Mark Renton through her. She is a student at a local college who tends bar to pay her school bills. Though Kelly is distrustful of all men, she and Renton spark a real relationship. She moves down to London with him for a while but leaves when she decides she can no longer afford it. In her last appearance in the novel, she is working at the pub where she gets revenge on a group of disrespectful men by tainting their food with her menses, urine, and feces.