I hear what you are saying. Most of my friends have kids and/or are married or are getting married soon, and they are all in their early twenties! It sucks when you feel like you are getting behind in the game of life, but I wouldn't worry too much. I know it's hard, especially when people who are younger are getting those things before you. I know this, because I have that too, I know girls who are like 18 that are getting married, and I am 22 and I can't even seem to keep a boyfriend for a long enough time to get to that stage, hopefully the guy I am currently seeing will be the one, but you never know :S
Plus my friends now exclude me because I am not part of the group anymore since I don't have kids so therefore am immature and don't understand life, apparently :/ Even though I am working hard in college to get my degree and certifications. I think you should go out and find some friends who are in the same position you are in. Ladies who are not married or engaged and maybe even single, who would like to be married soon. Share with each other support and help each other find guys. Even if you don't find a guy right away, it gives you someone to hang out with.
Also try to be good to your friend. I get that it sucks having people forget about you, but she is getting married and she is your friend. Try to support her however you can. If you act sour all the time, people will start distancing themselves from you. Besides, why rush into a marriage just to be married? Marriage is something that should be cherished, not rushed. If you wait, marriage will come to you and it will be the right time with the right person. If you rush it, you will end up regretting it and it won't be enjoyable.
I have felt how you have felt. It sucks seeing young girls having kids and having bf's for like 4 years when I can't seem to have that, and I am much older. I know nothing is wrong with me, I am smart and I have a life plan. Everything seems to be going the right way for me other than my love life. And there is no reason why a guy would not want to have me as his wife, I'm pretty awesome :P But I think you just need to realize that if a guy can't see your potential, then you are better off not knowing him anyway. The right one will come along, and when he does, you can be the one who is getting all the attention :)