Louise Bourget is described as a "vivacious Latin brunette" who began working for Linnet Doyle a couple of months before her death. Louise is the last known person to see Linnet alive and appears reasonably shaken during her interview with Poirot wherein she denies seeing or hearing anything to do with the murder. However, she does suggest, in front of an audience that includes Simon and Colonel Race, that "if" she had been awake and "if" she had been on the deck, she might have seen the murderer and been able to help with the investigation. Simon assures that he will "look after [her]," and immediately thereafter, Louise suggests that Fleetwood, an engineer on the boat, had motive to kill Linnet.
Soon after her offering her speculative statement, she is found dead in her cabin holding onto a Bank Note, which suggests that she blackmailed the murderer whom she witnessed leaving Linnet's cabin.
In the 1978 film version, Louise Bourget is played by actress Jane Birkin. The character is an amalgamation of the characters Louise Bourget and Marie from the novel. The latter character is omitted from the film. In this version, Linnet had discovered that the man she wanted to marry (an Egyptian) was already married. Unlike Marie in the original, Louise does not break off the relationship. She continued to persist. she wanted to resign and use her backpay as the dowry. Linnet refused but Linnet refuses to give her the promised final pay. She thus had a grudge which made her a plausible suspect in the subsequent murder of Linnet. She also blackmails the killers as in the original. Rather than stab her, Jackie cuts her throat and takes the money back only for one of the notes to rip. She is discovered after a crew member drops a towel into a pool of her blood.
In the 2004 Suchet film adaptation Louise Bourget is played by actress Félicité Du Jeu. The portrayal is closer to the book. Marie is not featured in this adaptation either but the plot element of wanting to marry an already married man is not given to Louise. She does have a grudge, though, because her boyfriend got landed in jail but Linnet refused to lend her money for bail. Like in the novel, she does blackmail and there is a scene told in flashback of her counting her money and then being stabbed. Unlike the novel, Louise is not found dead in bed. She missing at first and only found later when Poirot and Race search her room and find her in the wardrobe.