Clara LaGuerta is a minor character and a Stranger featured in Red Dead Redemption. She appears in and gives the player the Stranger side-mission "The Wronged Woman".
In witch John/Jack Marston finds her crying in a church, and she tells him she was seduced by her employer, Harold Thornton, and is now pregnant with his child. He fired her once it was apparent that she was pregnant, and Harold has since become an alcoholic. She wants Marston to find Harold and get a few dollars from him so she can prepare for the child's birth.
Marston, feeling bad for her, goes to find Horald who is at the bar. He will deny everything and seems confused, forgetful of ever hiring or knowing Clara (although he says he used to have a housekeeper named Sarah).
Marston lets this slide, and simply asks him for a few dollars so Clara can find a home. But unfortunately, Horald misunderstands and challenges Marston to a duel. You must kill him (no honor change), loot his body ($200) and go to Clara and hand her the money. She will then worry about his death and run out, yelling "maybe I can catch the funeral!".
Marston returns to the chapel's graveyard a few days later, to find a bereaved woman crying at his grave; the woman is Elizabeth Thornton, Harold's wife. She will talk about Harold, saying he was a good man and didn't deserve to die. She also mentions that Clara attended the funeral laughing, indicating that Clara had never worked for the Thorntons and was not impregnated by Harold, but instead used you to kill him and obtain the money for a different use. This can be clarified by reading the notes under "Strangers" in the "Stats" menu after completing this mission. The notes tell you that 'she conned you into robbing and killing Harold'.