I Sandrajo, looshead has made a point, a bit strong mind you! But it is always worth trying to examine if you have done something to hurt or offend others without realising it! However you seem from your question like a nice person and I will take you at your word! Here is my twopenny's for what it is worth!
I knew a girl some years ago, thankfully she was not one of my friends, although to me at the time she seemed quite a popular person. This girl did nothing but bitch about other people behind their backs. I was listening her her having another go at someone one day to one of her friends and suddenly the thought struck me that she was very sad and probably had no confidence herself as she had to bring everyone else down to feel better about herself. When I realised this about her, I started to look at her in a whole new light and realised that she was not as popular as I thought. I also found myself less and less bothered by her comments about others and after that I started to actually feel a tiny bit sorry for her!!
I would say that this new 'friend' of yours may be jealous of your popularity, has not really experienced it herself and is trying to bring you down by belittling you in some way? Your other friends know the real you, so if she is trying this, It won't work, so I would not worry about it!