Really disappointed in my Maid of Honor

My maid of honor and I have been best of friends since 6th grade. We're now 25 years old and have stuck together through thick and thin. To make a long story short, I asked her to get her dress by the end of Jan, which was 4 mths from wedding and they had a year to save. It was the end of Feb before I asked if she needed any help getting the dress. I bought the dress and shoes for her only for her to turn around and adopt a puppy that was more than what I paid for her dress/shoes. She didn't show up to the invitation party which I was disappointed but it wasn't end of the world. When she didn't show up to my bridal shower is when it broke my heart the most. I tried to share my concern and now she hasn't talked to me in a month and I have chose someone else. I wrote her a letter letting her know my feelings and that I still value our friendship but I don't understand why she would do this. I'm thinking our friendship is over and she won't be at the wedding :/