It's not okay to violate someone's personal privacy.
Cameron has a crush on his sister's friend and just noticed that his sister left her laptop open when she left the house.
Cameron wants to know what his sister's friend thinks about him.
Cameron waits until his sister gets back and tells her he likes her friend and asks what she thinks about him.
Cameron goes on his sister's computer while she's away and reads her chat logs with her friend.
Cameron's sister tells him tells him that her friend likes him as a friend but not really romantically.
Cameron's sister finds the chat logs open when she gets back and angrily confronts her brother.