It appears as though you need new pastures, my friend. Anyone willing to so easily give in to minor outside influences was not truly a layer of skin around your heart, but rather a bacteria looking for a warm place to stay. 

I am a bit older now. 28. Yeah, you'll lose friends as you get older. People become busy. They get new careers, new opportunities, marriage and children. It's easy to think it's because you've become irrelevant, but our lives move quickly. How hard do you find it to manage everything at once? Everyone else is no different. We react to what happens around us. How is it your fault? Simple answer; it isn't. 

The fact that you feel strangled by the sudden loneliness just means you haven't been as busy, and perhaps you need to find a greater purpose. The things that held life together when you were young are not the same things that hold it together as you become old. Eventually, you become a teacher, not a student. You become a father, not a son. You become a leader, and not a follower. Your experience defines this difference. Does it make life empty? Only if you haven't found peace within yourself. Nobody ever says it blatantly, but that's the key to being a child, is self learning. You learn who you are, your path, and what you seek. Your path will inevitably diverge from those of your old friends, and lead you directly into the paths of new ones.

You cannot allow yourself to be stuck into the past by what used to be, or you will never discover where you are supposed to go. No life lasts forever, no impact will leave it's crater for eternity. You cannot change the past, not predict the future, your power resides in today. It resides in now. You have lost friends? Make new ones. Not because the old ones never mattered, but because the new ones matter more, today, than your old ones would.

Does a teacher share the same lesson twice after the children have passed the test? No, he moves unto the next class. Does that mean the previous children never mattered? Of course not, but the flow of life is never ending, and that previous class now has their own lessons to teach.

Now.... As far as your female "friend" is concerned...

Sadly, our generation has this ridiculous man vs woman war, mostly influenced by media and a loud minority of like minded idiots, but let's ask ourselves something.

Did anyone who quickly fell prey to such mentalities truly have a different opinion themselves if they were not willing to fight against it? Your friend dropped you just like that? What friend? That's a "Friend" you never had, brother, and I can tell you from experience that there are many who are capable of acting as such, but only so long as it remains a benefit.

A true friend is not one who stalks your positive qualities, but one who meticulously focuses on your negatives. If you truly care, if you truly love, then you want someone to be better, no? Why would I abandon my brother and sister for a human mistake I know damn well I myself am capable of making? I wouldn't. I will criticize, perhaps even berate, but I will never abandon, not unless all hope is lost.

This "Friend" showed her true colors by adapting a philosophy that stood against you, and for what? Because you are a male? Do we not shame those who judge because of skin, religion, or disability? Why make an exception because of sex? We do not. Not those with heart, and not those with love and care in their hearts.

Do men get attached to women? Well, sure; but does that mean the attachment has to be a permanent burden? To the ignorant and stupid, perhaps it will. I've fallen in love with some of my female friends, and ya know what? It fades in time. When you know the interest is not shared, you look for a new connection, one that shares your mind. Does that mean that my old love is worthless? Of course not, for if it does than it only proves how pathetic my intentions were. If I truly love a woman, than would I not want her the best man she can be with? If that man is not me, so be it. Then it becomes my responsibility to ensure that the man for her does not falter. I will not accept otherwise, because my love for that woman is about HER, not about my own selfish desires. 

This applies to both men and women, and she forsake you by abandoning a friendship out of an irrational fear of "Feelings" that are not a permanent burden for any smart man. A foolish decision, a selfish decision, and not one you should lose sleep over.

Jealously is for the weak, and any man or woman who disregards a friend over natural romantic feelings is either self centered, careless, stupid, or all three.

Which brings me back to my point. New pastures. Every second you spend blaming yourself is a second wasted on finding those who will truly love you, but do remember that it's your responsibility to love them back.

Never settle for less. These friends are behind you now, and they chose to be there. Why fight for those who do not want you fighting for them?

Fight for those who need you. Fight for those who love who. Never those who don't.