Hibiki can be described as a demanding person, specifically when around her twin sister. Though she can appear quite mean towards Kanade, it's described to be Hibiki joking.  Despite this, however, it's a simple cover up, with Hibiki meaning what she says at times. Along with this, it's said she's always around Kanade, appearing to be the dominant out of the two, being "high and mighty", as described by Sora. It's believed she's easily frightened, however. It's also shown that Hibiki has the habit to give the others on Utsurohima an nickname of sorts which is used to show trust between her and that person.

Due to the stress and worries Hibiki was having during the early days of being on the island, she appeared to be more prone to lash out at people, as well as having outbursts mid-conversation.

After the Chapter 1 trial, and the revelation of Void, it's shown Hibki lacks remorse for Hajime, blaming him for starting the Killing Game. She's shown to quickly blame others as well, hinting at her loss or remorse over the current time spent on Utsurohima. With Void being revealed the day prior, it's apparent that Hibiki has developed a distrust for everyone around her, par Kanade, outright saying it in conversation. 

Later on in the chapter, it's shown the Hibiki's distrust only goes to a certain extent due to the nicknames she gives to the other participants. While initially rejecting the idea of performing due to her paranoia, she later went through with the idea, showing to have a more passionate side to herself when an activity had to do with singing. 

Appearing to blame herself for the deaths before the third, Hibiki attempts to act more confident and motivational, Yoruko initially thinking she had an alternate personality due to Hibiki's usual emotional reactions in earlier days. It's later described in Sora's thoughts that Hibiki changed the most throughout the time at Utsurohima, the latter developing a more mature personality.

Despite having a job and having many business relationships, her childish personality partially has to do with Kanade killing off anyone that has the potential to make her a mature person.

Honestly, I believe that the Official Voice is absolutely perfect for Hibiki. Absolutely attempt other voices for her, everything is welcome, however if you need a reference, I'd say maybe https://www.youtube.com/watch?v=HJ6-K3uxUEg  this?