Friend assuming she is a bridesmaid..

So I called one of my close friends yesterday to inform her I was getting married, which she was very excited and happy about, but the very first thing she says when I tell here is "OMG, No way! Am I a bridesmaid?" and I go' Well, we haven't thought that far ahead yet, Greg only wants 2 or 3' she jokingly says "what!? that's b/s!" I honestly do not want her part of the wedding party, I have a very bad feeling about it as most of my other friends and family would not and do not get along with her, How do I say this, She has a very strong personality and she's always right, has to one up you , etc. Don't get me wrong, I do appreciate my friendship with her, but I (and most other people) can only take so much of her, HELP! I've already asked my sister my cousin and best friend. So can I explain to her that I don't want to put her in the wedding party b/c I know she is struggling with money, and that she would be having to pay for a dress, shoes etc, hair and travel to the wedding con't..