Lily and Sirius headcanons?
Lily is one of the key reasons that Sirius’s beliefs don’t match his families. His whole life he used to ask ‘why are they so bad?” but no one would ever give him a straight answer until he met Lily and he figured it out for himself. They weren’t. Lily was smart, kind, intelligent, crazy talented and most certainly someone to be admired and it made no sense how his family could hate someone based on blood after meeting her.
They got partnered in charms together in first year because James and Sirius kept mucking about so Flitwick separated them. Sirius spent the entire class quizzing her about Muggle life, and she in turn quizzed him about Wizard life. It was the start of an acquaintance ship, but it wasn’t for another several years that they got to be super close.
In around fifth year Sirius developed the nickname ‘little ginge’ and it’s what he called her ever since. Sometimes he would call her Evans or Lils/Lily but not so often.
Lily hated his arrogance, and she hated how he could be cruel - particularly with Snape - and he hated how she was (in his mind) naive enough to believe that a friendship with Snape could ever end in anything but pain. Whenever Lily and Snape fought, Sirius would be the one comforting Lily while James ended up detention for hexing him.
Lily and Sirius would mock flirt constantly - even when Jily was dating/married. Like sometimes she would fix his tie and he would joke that if she wanted to feel him up all she had to do was ask. He would ruffle her hair, sling an arm over her shoulder and could be quite affectionate with her though they were never more than platonic friends.
When Lily found out Sirius had left his family, the first thing she did was throw her arms around Sirius and hug him. He tensed at first, but once his mind remembered that this was Lily, his compassionate friend who wasn’t pitying him or mocking him, he hugged her back. It kind of helped him remember that he had friends who cared about him; that blood isn’t the be all end all and just because his blood family so easily discarded him doesn’t mean he was worthless.
Lily used to joke that when she started dating/married James she was also dating/married to Sirius so he used to send her joking flirty notes and even got down on one knee and proposed to her once.
It was Lily who first called Sirius ‘snuffles’ because she used to joke that Sirius was like a vacuum cleaner - in human form and as padfoot. He sees food and eats food.
While Lily couldn’t fully relate, she could empathise to an extent because she knows what it feels like to be different from your family and be ostracised - especially by siblings - because of it.
Sirius really respects Lily as a witch, and even as an immature 5th year he knew that she was not someone to piss off because she wasn’t afraid to stand up for herself, or others or call people out on their bullshit behaviour. Lily admired his strength, courage and loyalty.