Professional writers can write pages of exposition without a problem, this is not too much, and 3 times as much would not be too much.
As a matter of critique; you are weakening your prose with too many fudge factors and emphasizers: with "usually", "more often than not", "Try as she might", "simply", "sometimes ... but infrequently", "even recognised".
I think "purposefully" should be "intentionally".
Bringing up the specific subject of her study feels out of place here; as if geology were the only reason she does this. That seems unlikely, and I feel like you are just trying to wedge that subject in a little unnaturally.
Even though this is exposition and past tense, you should try to make it feel more like the present; i.e. past tense but just happened.
As an example (but of course I'm taking liberties, so trying something like this in your own words):
Unlike the other girls from her town, Lillia took the early train to school, to give herself time to complete her homework. A year ago she'd given up on doing homework after school, it put her to sleep. Taking the early train was getting it done.
Once in a while she'd bump into Clara and they would walk in together. She recognised other girls from the early train, but there had been no friendships attempted by her or them. They had somehow silently agreed to not acknowledge each other's existence.
Today's assignment was on geology, rock layers in the Earth. Reading it on the train, she thought she'd have been comatose in five minutes if she'd tried it after dinner.
Added explanation: So more exposition can be done here. The main problem with exposition that people complain about is when you are dumping facts on the reader, that they feel like they need to memorize. To avoid giving that sense; you have your exposition occur while the reader's imagination is occupied with something else is happening: Lillia is getting on the train, riding the train, starting her homework, arriving at school, perhaps finishing her homework. That "action sequence" isn't a fight or a train crash, but it IS action, mentioned at various points along the way, and it glues together your exposition. Lillia is doing things.
More importantly, this is Lillia in the first half of the first Act, living her status quo life, dealing with her regular problems (getting to school and getting boring homework done without falling asleep, at the price of riding with strangers instead of friends).
What you want to avoid is situational fact dumps about "how we got here" or character history or character description. Those are boring and feel like stuff we have to memorize. But setting description, although stating facts, is welcome. If this were my story, I would add quite a bit about what the station looked like, what the train itself looked like, smelled like, sounded like, whether these are old or new, etc. This is all part of Lillia's world that shaped her and her attitudes, how she feels about these things let's us get to know her.
Also welcome are a few spoonfuls of history relevant to the task at hand, like why she is taking the early train, while actually boarding the early train. This tells us something about Lillia's mindset, that boring homework is important to her and worth sacrificing a morning hour with friends. So is the fact that she is working on geology, you could in exposition (or thought) expand upon that.
It was important because of course, in the adult world, categories of sedimentary rock are probably discussed every hour, she thought, with the sarcasm cranked to eleven.
Most authors will frequently go a page or more in exposition without anybody speaking, Harry Potter opens with four pages of exposition and only two words spoken, and those weren't necessary. But they are almost always exposition about setting, or while we "watch" a character doing something or experiencing something, or both.