All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
The Ahaadeeth reported in the authentic collections of Al-Bukhari and Muslim have received unwavering acceptance from the Muslim Ummah, as stated by An-Nawawi . Indeed, we have clarified this in Fataawa 21893 and 85547.
The Hadeeth which you mentioned in the question was reported by both Al-Bukhari and Muslim . Al-Bukhari included it in several chapters of different titles, such as "Chapter: The jealousy of women and their anger", and also "Chapter: Loyalty is an act of Eemaan", as the Hadeeth is related to these two topics. Al-Bukhari also included it in the title "Chapter: The virtues of Khadeejah " and so did Imaam Muslim in his Saheeh.
We shall cite the meaning of this Hadeeth with slight adaptation from Fat-h Al-Baari authored by Ibn Hajar : “ ‘Aa’ishah was jealous of the wives of the Prophet but she was most jealous of Khadeejah . She explained the reason for that saying that the Prophet frequently mentioned her. A woman is jealous of her husband loving another woman more than her, and the fact that the Prophet mentioned her frequently indicated that he loved her much. Al-Qurtubi said that what is meant by mentioning her is praising her. Khadeejah had died a long time beforehand, and `Aa'ishah pointed out that if she [Khadeejah] was alive at her time, then she would be even more jealous of her. Among the reasons for her jealousy is also that Khadeejah was singled out with the glad tidings – i.e. a house in Paradise – and this indicates that the Prophet loved her much. Also, among the reasons for her jealousy was that the Prophet used to slaughter sheep and give enough of the meat to the female friends of Khadeejah to cover their need.”
Allaah Knows best.