My Sister is a Liar! Maid of honor drama

So recently my sister got married. There's a host of problems there but I need to talk about the maid of honor. When she first got engaged she told me she didn't want a wedding party or a maid of honor because it would be just a small wedding. She continued to say that up until July.

We spent a whole day together, shopping and eating lunch. We talked about the wedding and she said she still didn't want a maid of honor. I got home and she went out to see family. I was checking my instagram when I noticed my sister in law posted a picture. She posted that my own sister asked her to be the maid of honor. I was confused, furious, and wanted to cry.

My whole family loves my sister in law, she's great, but we've known her for only five or six years. When my family found out that my sister asked her, everyone was pissed. I just didn't know if I was more upset over the fact my sister chose her, or the fact that she lied to me!

Fast forward a couple months, the wedding was a couple of days ago but right before I was speaking to my cousin. We're very close and I told her that I wanted her to be my maid of honor (I'm not getting married for a couple years) and she said yes! It became a running joke during the wedding, one to which my sister did not like. She was furious I would even consider

anyone else as my maid of honor. Hypocrite much?

Am I wrong somewhere? Should I just choose her? Help.