Girl Online (Girl Online #1) by Zoe Sugg

Penny has a secret.

Under the alias Girl Online, Penny blogs her hidden feelings about friendship, boys, her crazy family and the panic attacks that have begun to take over her life. When things go from bad to worse, her family whisks her away to New York, where she meets Noah: a gorgeous, guitar-strumming American. Suddenly Penny is falling in love - and capturing every moment of it on her blog.

But Noah has a secret too. One that threatens to ruin Penny's cover - and her closest friendship - forever.