You can deal with not revealing your feelings. You have to. In the course of life, there are a lot of things that are left unsaid. They have to be. For example, my mother's very religious. If I told her I've lost faith in religion, it would break her heart. So, I don't. I go to the masses.
Also, there's a girl I like. But I don't tell her, as you know. I can't. She's with my friend. The need to let it out cannot trump the unfairness to her. It's not fair for her or for my friend. Just like how you won't be fair to her or her boyfriend. There's a reason people don't do what you're thinking about doing. It's because it's unfair and a bit disrespectful.