Discuss with her when she is in a good mood but make sure that the discussion is in a healthy manner and not in a nagging way otherwise , she would get defensive . If she thinks that this is the problem then you can think on how to resolve it so first you should get her understand that this is not the right thing in the relationship and it could damage the relationship permanently . It would be better if you take the help of therapy to understand the pattern of her behavior . If you are unable to fix it after trying everything then you should think of leaving her but first explore all the options to save your relationship . <| sep |> grow the fuck up . this is one of the most natural things . if you are uncomfortable look away or leave the room or at least be a bit more sensitive in saying that you feel uncomfortable . something along the lines . sister , as much as i admire your devotion to your kid , would it be alright if you do this in another room and not while we at the dining table i guess it was that ? i would also be a bit uncomfortable but i wouldnt be so . i dont know . rude about it . i would offer her another place , maybe more comfortable and quiet for the kid . you see she is still 100 % hormonal after birth and you were just rude to her !