Who should apologize?

"J" asked to look at and explore her step sister's ( "C" ) husband's phone, thinking she might be interested in getting one like it. He gave her permission. When she opened the texting application there were some texts to and from his wife and another brother in law (the most recent texts) that said in effect how they all despise "J".

"J" thinks that they should all apologize to her for having said the things they did about her. She acknowledges that we all say things that are unkind or untrue about another person, but typically the other person never finds out. "J" says that because she found out and because they know that she knows, they should apologize.

"C" thinks "J" should apologize for snooping around in her husband's texts on his phone. She acknowledges that they were saying mean things, but that it serves "J" right for snooping around on her husband's cell phone.

Who is right?