Completely normal. Where I live, they usually sleep together bottomless too.
http://imdb.com/user/ur2019270/ratings

also you mind want to read about a psychoanalyst called Sigmund Freud, he basically had the idea that babies derive pleasure from feeding, and thus have what's called an oral fixation. This is why babies put a lot of things into their mouths. Some think this could be related to people deriving pleasure from eating.
Freud also thinks that this pleasure could be also experienced in a sexual way. Some even think that the baby has sexual needs, and that boy babies and later young to adult males feel sexual towards their mothers, and this he called the Oedipus complex. There's also a case where girl babies and later young to adult females feel sexual towards their fathers, and this Freud called the Electra complex.
Freud thought that there was a drive towards creation, sexuality or eros.
Freud thought that there was a drive towards destruction, death or thanatos.
Freud had some pretty odd ideas. like the Oedipus and Electra complexes, but also obsessions with men finding phallic symbols. He believed women when they had PMS were suffering from hysteria, or lunacy, based on hyster meaning womb and luna meaning moon, meaning the monthly menstruation cycle. He also thought women thought of themselves as deficient men and that they had penis envy.
He had odd ideas, but they were the beginning of attempting to understand the motivations behind behaviour in the mental processes of the brain, and thus from this psychology and psychiatry was born.

Her sister was having a mini-breakdown and so I suppose comforting her was the utmost in her mind.

How do they turn off the sexual while breast feeding? Simple. It hurts like hell!

what are you saying? are you saying that boobs should only be for sucking on in a sexual way? or are you saying that boobs should be used for neither sexual sucking on or breast feeding?

Because there is no god, and nature made boobs for sucking milk from and nature tends to make things feel good to trick you into doing what's necessary to continue the species like sex and breast-feeding. A woman's breast generally enjoys being kneaded and sucked on and the body doesn't really care what's making the motion.

actually there is something inherently sexual about boobs. after all they are private parts, covered by most people in the world traditionally throughout all times except for caveman times and maybe Roman or Athens times and African tribes. also, they are sexual in that women get pleasure from people touching, licking, rubbing, caressing, groping, holding, squeezing, sucking, or fuc#ing them.
what I dont' understand is why did God make boobs both sexual and maternal? I mean I find it extremely unsettling and disturbing the idea and thought of having sexual fantasies about the same thing that babies suck on. and also if they are both sexual and maternal then how do women turn off the sexual while breast feeding? how do they compartmentalize those two things in their mind and psyche?
but yeah I agree that boobs should be showed more everywhere. and I also agree that people in America are ignorantly brainwashed into being ignorantly ashamed of and insecure and unhealthily uptight about sexuality and nudity.

they're just boobs - baby feeding devices - there is nothing distinctly sexual or private about them. It's not like the girls were slapping vaginas together.

The film didn't exactly depict "normal" events though, did it?
And believe it or not, there are vast regions of the world - I would guess
very
far from where you live - where people haven't been indoctrinated with the idea that exposing their bodies to others is shameful.