[Salander's] mother [Agneta] had spent ten years at Äppelviken, and it was where she finally died at only forty-six, after one last annihilating cerebral hemorrhage. (5.1)
At this point, we still don't know what happened to Salander's mother to put her in a nursing home so young and cause an early death. (She died in Tattoo.) This quote tells us that Agneta is only a few years older than Blomkvist when she died.
As a teenager [Salander] had cherished the fantasy that her mother would get well and that they would be able to form some sort of relationship. (5.3)
We don't get Salander's memories of interacting with her mother before Zala beat her so badly that she suffered regular strokes. This thought make us really curious about those times. This quote also makes us see how much Salander's missed not having a mother in her life.
She had no reason to love this apartment. She had moved in with her mother and sister when she was four. (7.37)
That means that the apartment Salander was living in all through Tattoo was where Agneta was brutalized by Zala and where Salander tried to kill him twice. It also means that where Mimmi was kidnapped is roughly the same spot where Salander set Zala on fire. Creepy.
[Salander] wanted to spend the money on something that could make her mother happy. She walked to the post office […] and sent an anonymous donation to one of Stockholm's crisis centers for women. (7.73)
This is our first major clue that Agneta's strokes are related to domestic violence. It also suggests that Agneta had some interest in preventing violence against other women. This would seem natural, but some of the other quotes below make her seem barely aware that she's in a terrible relationship with Zala.
And why had [Palmgren] not contested her declaration of incompetence while he still had the power? He knew why – he had wanted, selfishly, to keep his contact with her alive. He loved this damn difficult child like the daughter he never had, and he wanted to have an excuse to maintain the relationship. (8.129)
Truly, Palmgren is the closest thing to a loving parent Salander has ever had, and she knows it. Many parents do things (which could be construed as selfish) to try to keep their children safe and close. But that still doesn't make it right. In his defense, he does decide to get Salander out of guardianship, but the stroke interferes.
[Mia] wondered whether it was the right moment to interrupt his conversation. Her period was three weeks late. She had not get taken the pregnancy test. Perhaps it was time. (10.50)
This is the only hint we get that Mia could be pregnant. If it's in her autopsy report, we don't hear about it. But knowing that she might have been makes her death seem all the more tragic.
[Palmgren] "Lisbeth and her twin sister Camilla." (28.99)
[Blomkvist] "Good God – there are two of her?" (28.100)
"They're very different. But that's another story." (28.101)
Likely, Larsson was saving Camilla's story for later books, because we don't get it the other novels in the trilogy either. That's one of the most frustrating things about this saga, if you ask us. We really want to know Camilla's story.
"They never did marry, but in 1979 she changed her name from Sjölander to Salander. That was, I suppose, her way of showing the belonged together." (28.101)
This suggests that Agneta was in love with Zala. Agneta and Zala began their relationship in 1977. Salander and Camilla were born in 1980, just after the name change. We wonder a) if he was beating her before she was pregnant; and b) what stopped them from having more children during the next twelve years.
Palmgren to Blomkvist: "And then her mother told her than Zalachenko had forgiven her everything." (28.131)
After Salander stabs Zala while defending Agneta, Agneta still thinks Salander is the one who needs to be forgiven. This suggests that Agneta a) doesn't blame Zala for hurting her; and b) doesn't seem to think it might be a good idea to get her daughter out of the house; or c) is so terrified of Zala she thinks that it's safest for all of them not to make waves.
Daaaaddyyyyy, I'm coming to get yoooou. (28.166)
Salander isn't one to get sentimental about blood relations. A bad man is a bad man.
Salander: "Does he know we're half siblings?" (31.82)
Zala: "Of course. But if you think you can appeal to brotherly love, forget it. I'm his family. […] And he isn't your only sibling. You have at least four more brothers and three sisters in various countries." (31.83)
This one shocked Shmoop a little bit somehow. To learn that Salander and Niedermann are brother and sister and that she has seven other siblings! Wow. It really is a shame that Larsson didn't get to finish his plans for the Salander/Blomkvist saga. At least a few of these other siblings would surely have popped up!