My friend's friend is annoying and desperate?!?!?

She is nice but annoys me and clings to my friend because she hasn't got friends in her own form. She ties her hair back tightly and it is greasy and she eats chocolate heaps, yet she is desperate for a boyfriend. I told her to ditch the puppy-fat, chop her hair and become cooler. She cut about 2 inches off her hair and then it went back to it's original, tied back ickily style. It makes her already plump face look plumper. She doesn't ditch the food. My friend says it's because her parents eat heaps and she has to. My friend is always making excuses for her. She hates it when I even come close to mentioning her friend's weight. The friend of hers has a terrible copycat fashion sense. She squeezes into the latest fashions combined with tight jeans, frills, scarves or even her studded denim waistcoat. She wears it all the time. My friend encourages her and says it suits her. Unfortunately, it doesn't really. I want to help this poor loser girl find a boyfriend, a fashion sense, a great figure and healthy lifestyle and her own friends, but my friend keeps gong on about how we only need to worry about stuff like our weight when we are older. Me and her friend were chatting and I was giving her tips on how to loose weight without going on a strict diet but my friend kept cutting in and complaining about how we are too young to worry about weight. What do I do? Should I try and be friends with my friend's friend? Should I not get in the way and leave her to be a loser? Should I help her? What do I do?