Things didn't stay that simple, though. They couldn't. Even she knew that. Even back then.
Brittany couldn't stay patient, for one thing. And why should she? Santana had been the one who'd kept telling her that it didn't mean anything, or at least, that it didn't mean everything. Even if everything in her actions spoke otherwise, her words kept saying, "This is not real. This is not serious." And so eventually, Brittany moved on.
Santana tried not to let on the way it cut her to the quick, the way that seeing Brittany truly happy and out in the open with someone else made her feel like she was being cleaved flesh from bone. Being hurt meant that it mattered, and it wasn't supposed to, or at least that's what everything around her told her. According to the world she lived in, whatever she'd had with Brittany, whatever she might have with another girl sometime in the future, didn't count, except to count against her. And so she did her grieving in secret, buried it deep in her chest, and then—just to throw people off the trail—started a rumor that she got a boob job over the summer.
It gave people something to talk about, and even though her bra size hadn't changed in the slightest, no one doubted it for a second. It's amazing what people will believe about you when they really want to.
For a while, she even entertained the idea that being without Brittany would make it go away, that difference she felt between herself and everyone else around her. But of course that wasn't true. It was just as much a part of her as it had always been, but at least without Brittany there was less of a chance of being caught.
She actually was never all that worried about how her parents would react if they found out. They'd always been fairly liberal and open with her about those sorts of things, and her mother had fairly strongly hinted that she'd be there if Santana ever wanted to talk to her about her "friendship" with Brittany.
It was everything else that was the problem. Not just the stupid kids at McKinley, or even the rest of her family. It was that the whole ridiculously-named process of "coming out" just seemed so invasive, so tedious. She didn't want to be the subject of pointed looks and hushed whispers. She didn't want to answer any questions or have any heartfelt conversations. And she certainly didn't want to be anyone's poster child, for good or bad.
So she had chosen to keep quiet for the time being, until graduation at least. To get through each day and carry the secret forward to the next, until the time and place felt right to deal with it. It wasn't a perfect plan, but it seemed workable enough, until Finn Hudson had come along and ruined everything.
Maybe she should have been more careful, since she was obviously the one with more to lose. But Finn was a jerk, a malignant parasite that had sucked the life out of Quinn, then Rachel, then the Glee club as a whole. And she was just so tired of people treating him like he was untouchable. So she'd shot off her mouth for a while; then he'd fired back. And when the smoke had cleared—well.
She knows there are still people who think she deserved it; sometimes she almost agrees with them. Ultimately, it doesn't matter. It happened; she survived it. And that fall she left Lima and that life behind for what she hoped was forever.