AITA for making my roommate feel uncomfortable?

I (20F) and my best friend, Elaine (20F), have been best friends since we were kids. We are very similar people and see eye-to-eye in most situations. Because of this, it is easy for people around us to think that we are ganging up on them since we are always agreeing with each other. Elaine and I are also very good friends with Sara (21F) and have always seen her as somebody who has our back as we have hers. After having a nightmare roommate situation last year, we were excited for our two friends, Sara and Macy(20F), to move in with us. A few months before moving in, it was Macy’s birthday dinner. Me, Elaine, and Sara all drove together to attend the dinner; however, Macy informed us that she didn’t know the restaurant was so far and that she was going to be late. After sitting around waiting for her for around an hour, we began to get a little frustrated. The dinner went well; however, she and her friends had planned to go to karaoke in a bad part of town afterward. We had told her that we wanted to celebrate with her; however, we did not feel comfortable going to karaoke afterward. After this night, everything between us and Macy seemed to be different. Upon moving in, she did not seem happy when we would ask her to clean up after herself in the kitchen. Other things began to frustrate us, such as her boyfriend overstaying his welcome without giving us a heads up. It had become a very repetitive instance where we would have to ask her to clean and ask her to let us know how long her boyfriend would be staying with us. Elaine and I had gotten very frustrated with her and had made some snarky comments. We had since apologized and admitted our lashing out was childish. Things still felt a little rocky between Elaine, Macy, and me; however, we didn’t think much of it. On the other hand, Sara and Macy had gotten very close and began talking a lot more, leading Macy to feel comfortable talking shit about us to Sara. When Sara told us about this, we got incredibly frustrated with her and accused her of being a bad friend to Elaine and me, and got super upset for not having our backs when she talks about us. (She says she doesn’t like the way that we ask her to clean and make snarky comments.) We got very angry with Sara, questioning why Macy felt so comfortable saying these things to somebody we thought was our very good friend and wondering why she even told us in the first place. (IMO it’s completely fine that they are talking shit, it’s normal we are college girls, but you can’t tell us what the other person is saying and get upset). Should Elaine and I just let it go since it’s normal to talk shit? Are we right to be mad at Sara? Does Macy not feel comfortable talking to us about things that bother her because we seem like we gang up on people? I hope this story makes sense, as there are obviously a lot of excess details that play into all of this.