Here's my attempt at a correction, with explanations (I'm curious to see what native speakers will think of MY corrections!). I also incorporated my suggested metaphor of a hockey game -- obviously, if you want her to have a 44-year-lifespan divided into quarters, the numbers will be different, but the grammar won't change much.

Уже рассказывалось, что Светлана считала одиннадцать своим особенным числом. На самом деле, её короткая жизнь, всего тридцать три года, можно делить в равные трети, как три периодов в хоккейном матче. Когда Светлане исполнилось одиннадцать лет, старшая сестра перешла переехала в большой город и после потом вышла замуж; спустя одиннадцать лет, когда ей было года двадцать два, сама Светлана вышла замуж и стала матерью, и в том же году её родители умерли. В тридцать третьем году три года, она сама ушла этот мир.

It's already been mentioned, that Svetlana considered eleven her "special" number. In fact, one can divide her short life -- just 33 years all together -- into equal thirds, like the three periods in a hockey game. When Svetlana was 11, her older sister moved to the big city and then got married; when she was about 22, Svetlana herself married and became a mother, and her parents died that very same year. And at 33, she herself left this world.

NOTES:

I used рассказывалось (literally, "the story was already being told") because I thought it might sound stylistically better.

всего тридцать три года -- here всего emphasizes the sum or total

...исполнилось одиннадцать лет -- the verb исполниться can be used with number of years plus the person in the dative case to express "someone has turned so many years old". I used it here just for the sake of variety, instead of saying когда ей было... ("when she was X years old") every time.

перешла переехала -- presumably, she didn't WALK to the big city, but traveled by some sort of vehicle!

спустя одиннадцать лет -- "eleven years later; after 11 years" (very literally, it's more like "11 years having gone down"... down the drain, or down the hourglass, I guess!)

после потом -- the preposition после ("after") must be followed by an explicit noun or pronoun in the genitive (after WHAT?). In this case, you could use the prepositional phrase после этого ("after that"), but it's better to use потом, which is a "self sufficient" adverb by itself, instead of a poor, naked preposition shivering in loneliness without a (pro)noun to keep it company -- it means "after that" or "then" or "next".

ей было года двадцать два -- simply by inverting the word order and putting the noun (года) before the number, you can indicate "approximately"; thus, "she was about 22 years old". Also compare через пять минут ("five minutes from now") and минут через пять ("in, um, about five minutes, give or take...")

В тридцать третьем году три года -- the crossed-out expression would imply "in 1933" (or 1833 or 2033, whatever century she was born in). In other words, the 33rd year of the century, and not "at age 33," which is the meaning you're going for.