I meant that I'm attracted to her and I'd like to be with her, but I can't and I can't tell anyone in my life about it because I feel that'd be unfair to her and our friendship.
I feel your pain, brother. I've been in that situation more times than I care to count. Sometimes it's due to poor timing on my part -- admiration from afar and then when I finally screw up my courage to approach her
that way, I learn (just in the nick of time, and usually by total accident) that she is currently involved with someone else. So I have almost never had to experience the embarrassment of having the
"I like you, but I'm seeing someone else" talk. Which is good for my ego and enables me to "save face"...but it still sucks a bit.
My worst case of this was when I was invited to the wedding of a lady who I had had my eye on for some time, and we were (and remain) on good terms. So we got to talking pre-ceremony and she let drop that if only we'd been able to see each other more often perhaps we could have been a couple, because she liked me too...only that her now-husband actually stepped up and did the deed. That was a tough one

A nearly-as-bad case was a woman who started out as a (social media) friend-of-a-friend and now is one of my very best friends. I joke with her all the time that, since I can't have her (she's a very happily-married wife & mother), she'd better work on a cloning machine because she is just about everything I'd want in a woman. That one was a mutual case of "Where were
you 10 years ago? Because if you and I had been in the same town, we'd be married with six offspring by now"
When you're in that situation, the only honorable thing to do is to go home and lick your wounds. You have to uphold the sanctity of her current relationship. Don't be that guy who tries to break up someone else's relationship in order to get your turn at bat. Karma has a way of biting one rather badly, and you don't want to be on the receiving end of it. Do unto others, and all that.
So, yeah...I feel your pain.