I've got to agree in part with NSUballer here.
While i know how a girls friends can alter how they view a guy, even how hot they think he is, the attraction level is still decided by her. And when she's with a guy, it's decided by how he is making her feel... which is partly how she is percieving him and how good he is at making her feel specific emotions.
Of course if she hears her friends say her guy doesn't look so good she'll begin to question that, and if she begins to associate negative feelings to that appearance it can effect how much she'll feel attraction to him. It's all about how that women associates specific feelings to specific looks.
That ties into the whole age thing to. As a woman ages her associations between looks and attractiveness changes based on her experiences.
Still you can't ever forget that all of our views on what is hot or not is controlled by not just us but by those around us. There are many posts and threads on this, so i don't think i should bore people any longer, lol.