Is this a form of mental abuse or is my best pal just a nasty vicious cow?

It sounds to me like she is a nasty person - do you really want to put up with someone who treats you like that? Friends are supposed to be there for you through the ups and downs. Personally I wouldn't bother with her anymore, you will find someone who treats you with the respect you deserve; both as a friend and when you find the right man; as a girlfriend. sounds like it's time to get rid of the bad rubbish