Argh! I sat here and typed a massive answer for you and answerbank went all funny on me and I lost it! It was that long (2088 words) that I was having to do it in two posts!
Ok heres the short version, basically I have a friend just like you, so many networks of friends. As a result she never needs to try as such with any of them as theyre always calling her to arrange to do this etc and when she was first like this with me I did take it personally and was upset but soon learnt she never meant any harm and thats just the way she is.
You friend is rather petty ,I think, in thinking you arent giving her enough attention......she is not your husband, your child.....she shouldnt be demanding your attention. I am assuming you have tried explaining why you have things to be doing, etc. If not, you need to whether she is prepared to hear it right now or not.
Maybe sit and write a letter to her, explaining how upset you are at you two falling out over this and surely having each other as friends whenever you can is better than not having each other as friends at all? Then pop it through her door and give her time to read it and think about what you have said. Im sure she will soon be calling you, if not, make the effort to call her to show you still care about her and still wants to be friends.
Everyone has numerous mates, but you can usually only count your true friends on one hand.
Good luck :)