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In the past month, Emma Coronel Aispuro, the wife of the drug lord known as El Chapo, has become a controversial central character in her husband’s trial.

A witness named her as a co-conspirator in his infamous maximum-security prison break in 2015. Transcripts of text messages between the husband and wife showed him asking her to stash his weapons ahead of a raid. The morning one of El Chapo’s mistresses took the stand, Ms. Coronel and her husband wore matching maroon velvet suit jackets in what appeared to be a show of solidarity.

Over the course of Joaquín Guzmán Loera’s three-month trial, witnesses for the prosecution have described a grim life for the women in and around the cartel who are often expected to balance a role that walks the line between lover and accomplice. Most fail, usually wanting to be too much of one, and not enough of the other. They often end up behind bars or in hiding.

But Ms. Coronel, the most prominent female presence in a trial of almost exclusively male players, has emerged as the exception.