Was Nina being sexually abused by her mother?

I had that feeling. When I bring it up it makes people uncomfortable of course, but I think there were many elements of this. I also saw that article you shared and thought it was accurate.

I never felt she was being sexually abused. But I do think her mom damaged her emotionally by being overprotective and controlling.

No. She was not.

No but her Mother is abusive to her though, it was not shown in the film but it was hinted in the way Nina behaves with her Mom. There is a passive aggressive vibe in certain scenes (the ''cake'' scene most notably) where the Mother is showing her hostility towards her daughter. It actually bleeds over in the scene where as in others it's bottled up.

I get the impression there was a fair bit of physical abuse when Nina was younger. Even physical abuse as an adult. Her Mother was also ''arresting'' her emotional and sexual development. She tried to keep her at the emotional age of about 12. Also some jealousy, my guess is that Nina was about 23 and the Mother in her early 50's and was jealous of her daughters career and youth. A career the Mother once had but never the talent or the success to her Daughters level.

I don't think so. I just think her mom was over-controlling about Nina's appearance, in a sort of narcissistic way. She wanted Nina to be physically perfect, because physical perfection and beauty is what was required for her dancing career and to take on the role of becoming the black swan. I didn't get the hint of any sexual abuse at all. In fact, on the contrary, I think Nina's mother wanted to shield her from all sexual thoughts / behavior, because she wanted her to strictly focus on her goals in dancing. But in the end, her mother's over-controlling tactics failed, because Nina couldn't deny her primal urges.

I remember wondering if her mom even existed or of she was a figment of Nina's imagination.