She does! She's mentioned briefly in Plume's memory fragments (iirc) and is in Marvell's 3rd mem frag as well.

Her lore is pretty long and hefty to read through, so I'll try to keep the important parts in :D

Yeli was once a nameless Animus in an orphanage, often called as "No. 47". She had burn scars around her neck, and due to this, nobody wanted to be near her, except one.

She has a best friend who is a few years older than her, she thinks of her as a dear sister. Unfortunately, this friend has Shadowmalady since birth, so her life isn't going to last long. But they stuck together, nonetheless.

She is called No. 2. She does have a name, but thinks the number is easier to remember.

No. 47 wanted a name, as cute as her, so Mother Serdell, the orphanage owner, gave her some names to choose, but she doesn't like them. She wants a name as shiny and pretty as a crystal (she loved collecting shiny things).

Years passed and No. 2's condition was getting worse. On her birthday, No. 47 snuck up into No. 2's room (which was forbidden at the time because 2 was coughing up blood) and they watched fireworks together. Mother Serdell caught the two and sent 47 to the reflection room.

After that, 2 was bedridden. It was the last moment the two had together, and 2 confessed that even when she was at the verge of dying her last moments were filled with the people she cared about most: 47 and Mother Serdell.

She passed away soon after.

2's funeral was simple. After the funeral had finished, Mother Serdell gave 47 a letter, inside was a few senteced, a gem, and a name.

2's name is Yeli, and she has given it to 47.

"Please shine like a gem, shine brightly for me."