Physically, she has long blonde hair that reaches just a bit past her shoulders and green eyes. She is 13 years old and is said to be too short for her height, being even a bit shorter than her brother Kuro, who is 10 years old.
Her character item is a lemon.
When among strangers, she's the really shy type of girl, and it's hard for her to make new friends because of this. But she cherishes the ones she has now and tries to be act as nicely as she can toward them, often being described as too good for her own good.
She is also said to fall for others easily, but nothing serious. Just perhaps, a small crush.
Like mentioned before, she's Len's daughter, but she's not Rin's. She has no oficial mother (At the time, the Len roleplayer who helped creating her was single, and they could never find an actual mother. This actually comes in handy when it comes to pairing wars.) You can make her the daughter of anyone you like in fan work, though Gumi would be a good choice, as Rinna has her eye colour and gets her voice from her (and a Gumi roleplayer was a good candidate to her mother, but she and the Len never actually confirmed it).
Example of her voice: http://www.youtube.com/watch?v=AnfeJrD3ho8