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 questioner is permitted to mention such expressions to one of her sisters, intending to teach her how to treat her husband to gain his affection. It is justifiable for two reasons:
First: those expressions do not reveal the husband’s secrets.
Second: it is permissible, in the course of education, to mention what is in principle forbidden, such as words and states of intercourse. In a Hadeeth on the authority of ‘Aa’ishah it was narrated that she said: “If the two circumcision organs meet , Ghusl becomes obligatory. I did it together with the Prophet, sallallaahu ‘alayhi wa sallam.” [At-Tirmithi; Al-Albaani: Saheeh]
According to another narration, it was narrated that she said: “I used to make Ghusl with the Prophet, sallallaahu ‘alayhi wa sallam, from one container, both of us were in a state of Janaabah. He used to order me to cover my private parts so that he could caress me when I am menstruating.” [Al-Bukhari]
Anyway, if the questioner teaches her sister those expressions without letting her know that she says them to her husband, it will be better.
Allaah Knows best.