One thing Ive noticed a lot of people who start out anime characters make the mistake in is the honorifics. Like the above anon has said, Rukia is rough here and there but also pretty formal. Most of the time her honorifics are limited to addressing senior officers, otherwise she sticks to last names (calling Orihime "Inoue" being an example of this.) I suppose it doesn't matter if you are going by the english dub. But yeah she can be shy and a bit awkward but also not too so. Don't be afraid to play up her love of stuffed animals! Also, don't be afraid to also have her talk roughly with someone she might not get along with or even someone she's starting to really get along with (calling them idiot etc.) but don't go overboard with it because she's not rude she's just... rough. Have fun with her art stuff and have fun with just her personality really. She's pretty easy going as far as Bleach characters go.