Rachel Vanessa Ryan was born to two pureblood wizards in Dublin, Ireland. Her childhood was rather chaotic - she was constantly moving around the United Kingdom due to her parents' work demands, and never stayed in one school for too long. As a result she never formed any friendships to speak of, and her only actual 'friend' was the piano that was taken with them in every move. She also took a liking to running by herself as means of expending extra energy, as their neighborhoods were mostly safe and/or magically protected.
The longest time she's been at a school was when she was in Hogwarts - for three full years, she was in the Gryffindor house. She was somewhat alienated from her peers despite the sense of camaraderie and her successes in Quidditch, becoming an alternate player for them in the first year, and quickly rising to a main roster position in the second.
Just as she felt like she could start fitting in, her parents were assigned to New York, in the United States. Rachel was transferred to Ilvermorny, and drafted to the Pukwudgie house. The process repeated itself - except she felt herself growing more withdrawn, and more verbally abusive. She didn't even stand a chance before her parents had to move again to Toronto, taking her along and forcing her to take a year off of schooling.
They were in a Muggle community that time, and so she had to adapt. Being used to being a Beater in Quidditch, she had an easy time taking up baseball and found out she actually enjoyed it. The introduction of Muggle (and, unfortunately, Internet) culture made her temporarily mellow out and form a few bonds, for as fleeting as they were, which made that year and a half go by a bit too fast for her liking. And as her life usually dictated, any feelings of settling in at last were soon followed by being uprooted. It happened then as well, and she was moved to Australia.
By that point, Rachel was visibly angry over moving so many times - her parents opted to sign her up to Tallygarunga and leave her there regardless of where they may end up, something she honestly doubts will happen. Due to different in school times she applied just before the school year was about to end, and was accepted in to the fifth year she had already completed for the sole purpose of an examination of talents and knowledge to ensure she was prepared to take on the sixth year. With abundant free time, all there's left for her to do is to aimlessly roam the campus, as well as Narrie, and endlessly torment the people she comes across.
The more time that goes by through that sixth school year, the more Rachel is coming to realize not a thing will ever change for her. Even if she found someone to latch herself onto much like a minion (begrudgingly - she's yet to forgive Lisa Knotley over the fact she's dating the Captain of a rival Quidditch team), she still fell on the wayside while everyone kept strengthening their relationships around her. Rachel's feelings of worthlessness are being exacerbated greatly, even if she herself doesn't realize it; and with the lack of initiative on her own part, things look bleak.