One of my used to be close friends is expecting to be my maid of honor. We stopped being close friends because she needs to be the center of attention all the time throws a hissy fit every time she doesn't get her way and tends to treat me like crap. Over the past year she had started to hang out with her partying church friends so I didn't really worry about it, but when she found out that my husband and I are going to be having our formal wedding she started insisting that she be the maid of honor.
I ignored her at first but now she's insulting all the people I've enlisted as bridesmaids. When she found out that it's generally each of the bridesmaid’s responsibilities to pay for their own dresses she informed me that she would not pay for hers. When I asked her who was going to pay for her dress she informed me that I would be paying for hers.
I really don't know what to do about her since she'll end up going off at one time or another, likely when it will cause the most trouble for me. Not to mention she'll make me seem like a terrible person to everyone she knows and cause copious amounts of unnecessary drama. How do I solve this problem with as few repercussions as possible?