Need to find the name of this movie

I need help finding the name of a movie I saw 10 years ago. I remember some scenes not actor names ecc, the release year is from 2000-2009.

The movie starts with a mom and her daughter, -its propably xmas- mom sings her a song something like *mommy will come again nanana nanana* a melody we hear several times through out the movie. Then the dad arrives home. Mom takes girl on shoulder exits the girls bedroom, walks down the stairs and runs to the swimming pool, girl hits her moms back and tells her to let her go, mom throws girl in the pool.

Girl becomes adult, lives in a big house in a city center like NY with skyscrapers in the background -propably the same one where the incident occured- and has a good relationship with her dad but not with her mom as she thinks she tried to kill her when she throwed her in the pool.
She propably works in a hospital -but Im not sure-. In a later scene, as the house is big she invites one of her female friends to help her find something in the house, they dont find it and they end up drinking wine and talking.

She may also have a boyfriend she met at work or elsewhere but Im not sure.

In another scene we see her now old mom dressed in a white nightgown that is depicted as crazy and scary walking in the corridors -propably in some of the floors of the house- under a red light and laughing in a sinister way. I think she spends most time in bed at the house as mentaly ill or in some sort of restricted institution as she is considered dangerous.

Later her dad -or maybe a therapist- asks her to narrate her childhood trauna regarding her mom. She talks about her mom taking her to the pool but then she stops as the bad memories come back to her. The therapists/dad tryies to calm her.

In the end we find out that her mom wasnt the bad one but her dad. Her mom actualy tried to save her from her dad when she throwed her in the pool. Then the flashback visions come back to her clearer and she understands that is her dad she has to protect herself from.

The main aspects of the movie are the first scene with the song and her mom throwing her in the pool, that is the heroins trauma, and the fact she finds out her dad is the bad guy in the end.