Anisakiasis: This is a parasitic infection caused by the ingestion of raw or undercooked fish containing Anisakis larvae. The patient's symptom of having a worm in her vomit is highly suggestive of this condition, as the larvae can attach to the stomach or intestinal lining and cause gastrointestinal symptoms.

Ascariasis: This is an infection caused by the Ascaris lumbricoides parasite, which can be ingested through contaminated food or water. While less likely to present with a worm in the vomit, it's possible for the parasite to migrate up the gastrointestinal tract and be regurgitated.
Gastrointestinal strongyloidiasis: This is an infection caused by the Strongyloides stercoralis parasite, which can penetrate the skin and migrate to the lungs and then the gastrointestinal tract. In rare cases, the parasite can be coughed up or vomited.

Intestinal obstruction: Although unlikely, a large worm or parasite could potentially cause an intestinal obstruction, which is a medical emergency. It's crucial to rule out this possibility to prevent severe complications.
Gastrointestinal perforation: Similar to intestinal obstruction, a perforation caused by a parasite could lead to peritonitis and sepsis, both of which are life-threatening conditions.

Diphyllobothriasis: This is an infection caused by the Diphyllobothrium latum parasite, also known as the fish tapeworm. While it's possible for the parasite to be regurgitated, it's relatively rare and usually presents with other symptoms such as weight loss and gastrointestinal disturbances.
Echinococcosis: This is a parasitic infection caused by the Echinococcus granulosus tapeworm, which can infect the liver, lungs, and other organs. Although rare, it's possible for the parasite to rupture and release its contents into the gastrointestinal tract, potentially causing vomiting with worms.