There used to be a fake account which had 600,000 followers (already suspended), but this account is the verified one, and her agency also admitted that's real. Within 8.5 hours of opening it, her followers count reached over 200,000.
With Oshima's graduation from AKB48, her Google+ account has been closed, and there will be much less opportunities for fans to see her, so this should come as happy news for fans.
Oshima's Twitter is here.
Source & Image: Oricon