Born in Erebor, 137 years ago, Ruili has never truly lived there. Her family being poor and filled with rascals mostly, were driven to a nomadic life out of necessity; necessity to survive and to escape some guards for some of her cousins. Since then, she has lived on a caravan. Having seen quite a lot of the world and having lived in less than comfortable situations, Ruili was molded into a firm caravan leader when her parents discovered they wouldn't have a son as they had hoped. 
Raised as if she was a son and not a daughter, she found herself with more freedom to roam than most dwarrowdam would experience, but on the other hand would find herself lying and doing all she could to keep her own gender a secret from her own kin as well as endure things she wished she wouldn't have to.

During their travels, her father found himself influenced by the race of Men and got strange ideas concerning marriage. While he had liked to ignore her true gender up till now, he made his position clear upon the matter. Like with the race of Men, as patriarch of the family, he had decided it was time Ruili served her 'true' purpose. To marry another and make sure to bring fortune and some respectability to her family.
Of course, this did not really sit well with her, but she knew that they truly needed this alliance. Yggril, son of Margril, was not a bad fellow and was pleasing enough to the eye. But he was not her One, nor was he interested in her. The marriage was terrible if you asked Ruili's opinion. Her husband arrived late, the vows were exchanged with tones worthy of a funeral and once it was acceptable to leave, neither of them found themselves in their common bedroom that night.

A year passed and Yggril and Ruili did attempt to have children: with no avail. This truly upset both families, but no one truly talked about it. Until her husband decided to leave for Moria, after hearing that a company gathered by Lord Balin had gone, seeking to reclaim it. Ruili was left behind to take care of a small caravan, that would separate from the larger group who would follow the son of their leader, in hope to discover riches beyond description. She honestly did not mind the freedom she had been given.
Until her parents died. Old age was nothing to be unexpected (even though they had all believed her father would have died by the hands of some bandit that wanted revenge), but it came as a shock to her. Her family-in-law took that as an occasion to tell her how much they were disappointed in the match of their son and herself. Ruili found herself slowly chafing at the continuous blames that befell on her and eventually snapped.

Oh, nothing truly drastic happened. But she had decided to follow Yggril, her foolish husband, and see if he was still alive. After all, thirty years had passed and she was not only worried (she had grown fond of him, in some strange sort of way, like one would be fond of their annoying neighbor that keeps on having better results in their garden), but also wanted to knock some sense into his head.
But she realized soon enough that she did not have the strength to follow her husband. And thus, it became time to train under the expert eyes of trustworthy folk.

Hearing rumors quite often from all corners of the world while traveling, she heard from the Elves of Duillond that a Regiment had been formed in Ered Luin many decades ago and that it still stood strong, under the watchful eye of Lord Dwalin, who was governing Thorin's Hall in the name of King Dàin of Erebor. Considering Elves rarely ever talked kindly about dwarrow in any kind or form, Ruili supposed that she should give them a chance.
In exchange, they gave her one as well. When she was accepted as a recruit, she did not expect much. Most dwarrow she had met so far had not shown her much kindness for having a different lifestyle than them, for not valuing gold and riches as much as they did. But the Regiment surprised her and went beyond her (meager) expectations. Since then, she has been steadily rising in strength and getting slowly, but surely, closer to her goal of Khazad Dùm. 

Recently, she arrived before the gates of Khazad Dûm and met with one of the former members that had been part of the caravan. He told her that her husband had died before even reaching Eregion, leaving her to wander aimlessly back to Thorin's Hall, having nothing to fight for no longer. She has handed over her caravan to one of the younger, but greatly capable dwarrow that was part of it and decided to remain settled in Ered Luin for now, until she found the energy to get on the move again.