Absolutely do NOT hire her for your wedding. You already have reservations about her skill and professionalism and she sounds like a total flake. There are so many other wedding photographers out there that deserve work more than she does. Is she even a legitimate wedding photographer, or is she mainly a family portrait photographer?
Bottom line- you want to have total confidence in your wedding photographer because it is a once in a lifetime event. You also don’t want to be stressed on your wedding day wondering if she is struggling with lighting, has the proper equipment, is missing important shots, etc.. Don’t worry about hurting Sally’s feelings because it isn’t about her and your fiance needs to realize it is important that BOTH of you are happy with the choice of photographer. When I got married several years ago, I remember allotting a pretty big portion of our wedding budget for the photographer, and I am so glad I did- especially when looking at our photos.