She Would Never Know...
Disclaimer: I do not own Hey Arnold, whoever does owns it.
Phoebe sometimes wondered why Helga thought she didn't deserve to know her biggest secret, that she loves Arnold. There's nothing wrong with the fact that Helga loves Arnold, just like how Phoebe loves Gerald. And sure both of them hide their true feelings towards these guys. Helga stays silent and yet can write romantic and passionate poems inspired by Arnold, and yet she won't tell her best friend about her biggest secret.
What really got me seeing the truth would be all the clues and hints of Helga like like Arnold. She would never know that I know her secret, and I will wait when she's ready to tell her secret to me. It doesn't hurt that she didn't tell me yet. When she's ready, than I will help her. Actually I will help her even now. She just would never know that.