LONDON — She was a sales clerk in a WH Smith bookshop at Heathrow airport, and when she wasn’t ringing up newspapers, paperbacks, and chewing gum, she was penning jihadi poetry on the back of used sales slips.

“The desire within me increases every day to go for martyrdom,” Samina Malik, a soft-spoken 23-year-old usually draped in a modest black headscarf, wrote on one receipt. A judge yesterday sentenced Ms. Malik, know as “the Lyrical Terrorist” for her Internet name and her poems celebrating beheadings, to a nine-month suspended sentence and 100 hours of volunteer work. She was convicted for possessing material ranging from a Qaeda manual to a reference work on “mujahedin poisons” and bomb-making instructions, which prosecutors said suggested the British-born woman’s linkage to violent extremists.

“You’re 23, of good character ’til now, and from a supportive and law-abiding family who are appalled by the trouble that you’re in,” Judge Peter Beaumont said. At an earlier hearing, the judge had confessed that Ms. Malik remains “a complete enigma to me.” The case comes amid a mounting debate in Britain over where to draw the line between terrorism and those who merely applaud it. Radical Muslim clerics have been sentenced to years of imprisonment for calling for the deaths of infidels. In July, three men were jailed for six years each for statements they shouted during an emotional demonstration over a cartoon depicting the prophet Muhammad, one of which was “Bomb, bomb the U.K.”

Ms. Malik was convicted over her terrorism manuals, not her poetry. But it is her verses that have captivated and horrified the public and sparked the row over when radical statements cross the line into inciting terrorism.

“It’s not as messy or as hard as some may think,” she wrote in her poem “How to Behead.” “It’s all about the flow of the wrist. Sharpen the knife to its maximum. And before you begin to cut the flesh, tilt the fool’s head to its left. Saw the knife back and forth. No doubt that the punk will twitch and scream. But ignore the donkey’s ass. And continue to slice back and forth. You’ll feel the knife hit the wind and food pipe. But Don’t Stop. Continue with all your might.”

Ms. Malik sat silent as the judge read out her sentence, twisting a tissue in her clenched fist. At one point, she buried her tearful face in her hands. She has claimed she was seduced by the violent preachings of radical clerics as she began exploring Islam and adopted the Internet moniker “Lyrical Terrorist” because it “sounded cool.” Though her writings appeared to revel in violence and condemned the nonbeliever as a “stinking kuffar ape,” she never meant any of it, she told the court during her trial. “This doesn’t mean I wanted to convert my words into actions,” she testified. “This is a meaningless poem, and that is all it ever was. To partake in something and to write about something are two different things.”

“Ms. Malik was convicted of collecting information, without reasonable excuse, of a kind likely to be useful to a person committing or preparing an act of terrorism.”