Lyra has always tried to avoid her brother and his friends during the school year. She didn't find anything wrong about them, she just didn't want to scare away the only people Sirius loved like family. Other than herself, of course. It had always been easy for her to do, even though Sirius had told her that it didn't matter to him whether she spoke to them or not. She was still worried she would scare them off, and she would regret it so much if she did that to Sirius.
By the time her fifth year came around, and she was due to hit her sixteenth birthday that October, she suddenly found herself being more open around people. Lyra wasn't sure why that was happening. It would be pointless to start suddenly building 'lasting' friendships, when they weren't going to last past her next birthday. She didn't want to bother with that. She was already going to have to leave her studies, brothers, and her parents. That was going to be tough enough, no need to add to the stress.
And no matter how much Lyra's parents seemed to dislike her, She still deeply respected, and loved them very much.
Sirius and her were very close, people found that they were complete opposites. Where he seemed to be a troublemaker at times, Lyra was quiet and reserved. All they're lives they have looked out for each other. Soon, there would be no need for that. Lyra hoped Sirius would be accepted by their parents when she was gone, maybe he would be able to understand what they did, they did because they thought was in her best interest.
After all, nobody was going to remember her. She was Sirius Blacks twin sister, Lyra Black, the Gryffindor girl that not many people socialized with, the girl that had always seemed to prefer being alone.