You don't get to forget the bad times. A tough and immutable truth. Especially when it comes to love, since it functions similarly to OCD. If you think you still love the person, but seem to be in control of it (especially if it's only an occasional doubt), you probably just need someone else as significant in your life. I appreciate that can be as difficult as trying to suppress doubt and indeed, love.
As for the problem with your friend, lots of people here might disagree with me, but I'm very much against expressing your emotions to someone who is in a happy and satisfying relationship. It only causes distress to your relationship with them most of them time, and discord in theirs. If your an asshole you can play that to your advantage, but I don't want to help someone do that.
If you think your absolutely, definitely, without a shred of doubt, deeply and emphatically in love, and it doesn't seem to want to wane, either seek help (really, it exists), distance yourself from her, and as a last resort tell her. (Notice how these are for extreme cases. Love is an an emotion, and like all emotions is irrational. Sometimes it can get dangerous.)
Age does matter here. I appreciate some people can have a relationship from their early teens and sustain it into adulthood, but very few can. If you are between 12 - 17 you're a lot more likely to feel intense feelings that are transient, but feel permanent. However because it is often as intense as love when you aren't emotionally compromised, you'll swear it's love for the rest of your life (or maybe you won't and I'm over-generalising). For what it's worth, it's not far off, and like I said it could sustain. Just think about it before you do anything. If there's a chance this will pass, and you can remain friends, take it.
P.S. If he's a dick to her, then I'd do something about it. That's me though.
Seriously, what is it with me and long answers today?
