Jo is a fictional character in the Marvel Comics Universe. Her only appearance was in The Uncanny X-Men

Uncanny X-Men

Uncanny X-Men, first published as The X-Men, is the flagship Marvel Comics comic book series for the X-Men franchise. It is the mainstream continuity featuring the adventures of the eponymous group of mutant superheroes...

#179.

Fictional character biography

She appears with the Morlocks

Morlocks (comics)

The Morlocks are a group of several fictional comic book mutants associated with the X-Men in the Marvel Comics universe. Created by writer Chris Claremont and artist Paul Smith, they were named after the subterranean race of the same name in H. G. Wells' novel The Time Machine. They first appeared...

 and therefore assumed to be a mutant

Mutant (Marvel Comics)

In comic books published by Marvel Comics, a mutant is an organism who possesses a genetic trait called an X-gene that allows the mutant to naturally develop superhuman powers and abilities...

, although her mutant power is never revealed. She appears only as Kitty Pryde's

Kitty Pryde

Katherine Anne "Kitty" Pryde is a fictional character that appears in comic books published by Marvel Comics. The character first appeared in Uncanny X-Men #129 and was created by writer-artist John Byrne....

bridesmaid. Her duty was to make Kitty presentable for the wedding ceremony. Jo always does what others ask and tries to avoid breaking the rules.