My advice is that girls are evil and not worth the time to worry about.
But if you decide you want to go against the above piece of sage wisdom, here's the next best thing... It has been my experience that if you like a girl, and she knows it, and you can tell that she isn't looking at you as date/mate material, you shouldn't be wasting your time on trying to change her mind. I can only think of one time amongst all my friends and aquaintances where it actually worked... The rest all end in either loss of friendship at best and fears of stalking at worst... and in all cases, a big waste of time and emotions. Were you down because she was talking about how great a guy he is, or were you down because she was complaining about him and punctuating every sentence with something that effectively means "why can't he be more like you?" If it's the former, stop reading this and just skip down to the next paragraph. If it's the latter, keep reading... Girls often seem to have this weird habit of finding a man who they think is the perfect guy... and not getting involved with him, but instead use him as a measuring stick for other men and then complain to him when she can't find one as good as he is. You may think she's hinting at something, but as I and countless other men can attest to, she's probably not, so don't fool yourself. It's just load of bullshit, and you'll see it a lot... Fortunately, not every girl is like this so there's still hope for you to find one who won't keep you in such an emotional bind.
Unrequited love really sucks. Unfortunately, it's a trap that is all too easy to fall into and in the end the only one you can blame for your misery is yourself for not having the clarity of mind and the willpower to see and overcome it... it blinds you to other potential romance that could have
real promise. Really, what I would do is find another girl who will be more receptive to you. You will be happier in the long run with someone who actually
shares your feelings.
Now that I've gone and spent aaaaallll this time typing, remember one thing above all the rest. Free advice is generally worth what you paid for.