Ben Daniels, Eva Benitez and Marcus use three different types of English. Ben, being a naturally born American, uses the typical Californian English. Marcus uses an African-American English, a type of English that normally shows the speaker's protectiveness or him/her raising an invisible wall when you're not "one" of them. As for Eva, she uses the gangster like accent when speaking. It is commonly heard from Latin Americans, especially those who are in a gang.
Erin Gruwell showed her power by not being afraid of her students even though they didn't show any respect towards her at the beginning. In fact, she even helped them open up using the Holocaust and a the journal she made them do on a daily basis. She became her class' guide in terms of changing themselves and opening up with each other. Ms. G. also showed her power by sacrificing her free time and make a ton of effort in helping her entire class.
Ms. G's class gained some power all because of her influence. Influence from her efforts of expressing her true self and by how she sees and treats people equally. Her students were inspired and started writing their own stories and they share their experiences to others through writing. From there, they gained a power through their journals and their writings and it is the power of expressing yourself freely.