Character Analysis
Antonina (Tonya) Alexandrovna Gromeko is a loving, supportive wife… to a fault. She's so devoted to Yuri Zhivago that she basically serves as his emotional doormat for a lot of this book.
We know from the start that Tonya's emotionally fragile. Take a look at the way she reacts to her mother's death, for example: "During the first hours Tonya cried her head off, thrashed in convulsions, and recognized no one" (3.15.2). Now, to be fair, a dead mother is a pretty big deal, but unfortunately, Tonya shows time and time again that sadness is kind of her default emotion, even in times when she should be angry.
Tonya is also mad jealous. The first time Zhivago ever mentions Lara in a letter, he hasn't even thought of her romantically. But Tonya's insecurities show through, and the very fact that Zhivago is mentioning a woman in his letters at all is enough evidence for her to call off her marriage: "In her letter, in which the construction of the sentences was broken by sobs […] Antonia Alexandrovna insisted that her husband should not return to Moscow, but go straight to the Urals after that wonderful nurse […] with which her, Tonya's, modest path in life could not be compared" (5.2.11).
Now, it's totally possible that Tonya is being sarcastic in this letter, which would go a long way toward establishing her as someone who doesn't take things lying down. But it seems like this letter is actually sincere, and that Tonya is ready to let Zhivago be with another woman at the drop of a hat if that's truly what he wants.
That makes Tonya pretty different from someone like Lara, who is more passionate and more willing to go after and keep the things she wants. Lara makes mistakes, yes, but Tonya hardly even gets the chance to: she's too busy being nice and following the rules.
We find more evidence of Tonya's doormat personality later in the book, when she writes Zhivago with the knowledge that he's living with Lara as if they were husband and wife. Zhivago has it in his power to track down Tonya and his children; he's just not doing it. Tonya's answer to this? "I do not blame you for anything, I do not have a single reproach; shape your life as you want it to be, so long as it is good for you" (13.18.16).
This one's a tough call. It's nice that Tonya is being a supportive wife, maybe, but we kind of want her to call out her husband for acting like a total jerk. On the other hand, maybe she just realizes that things aren't going to work out the way she'd like them to, and she's learned to deal with that. If she can handle war and deportation, she's a stronger woman than she seems, after all. She does understand that Zhivago and Lara don't want to hurt her, so maybe this is a genuine act of kindness and understanding.
Pasternak doesn't give a definite answer. Tonya and the kids disappear from the novel just about as quickly as Lara eventually does, and that disappearance should make us think. Why did this have to happen?
Tonya Gromeko's Timeline