Yes, she can be considered a Dandere character.
A dandere character is one who is normally quiet and silent, possibly to the point of coming across as emotionless at times, but will suddenly become talkative and sweet and cute when alone with the right person if they manage to push the right button to get them to pour their heart out, revealing that they're actually just shy.
A dandere will be more or less a normal person, but, will not talk unless spoken to/required to. They will avoid talking because of their shyness, but if need be, they will speak. Also, a dandere tends to feel more power in numbers. If they're with a group that they're comfortable with, then the shyness factor of said dandere will very likely decrease if another, unfamiliar person is introduced at that time.
At the first otaku meeting of Kirino, Ruri (a.k.a. Kuroneko) was silent and passed her time with her cell phone, but later when Saori introduced them to each other, Ruri was talking (quarreling) with Kirino.
Ruri was comfortable with Kyosuke. She was talking normally with him and
confessed her love to Kyosuke.
She also talks and enjoy herself when she is with members of Saori's circle and with school club.
These are, however, only some examples of her behavior. Throughout the entire series, there are many occasions where her character matches the description of a Dandere as stated above.