Am I overreacting?

So my best friend and I have known each other since middle school. We had a falling out in high school but reconnected years after. In high school she met a girl, we'll call her Sarah. Her and Sarah are close friends but my best friend is constantly talking shit about her. She's always saying Sarah is "disgusting" because she doesn't take care of herself or her body order. She's constantly telling me she's going to end their friendship and doesn't want to be her friend anymore and that their friendship is not good for her mental health. Sarah is always putting her in situations for example- they use to live together and Sarah's dog attacked my friends dog and in the process the dogs broke Sarah's $200 bong and she made my friend pay for it as well as the dogs vet bill. Sarah is also depressed and will beg my friend to clean her apartment for her where she puked everywhere besides the toilet. Anyways, my friend will say all these things and then 2 days later post a picture of them together to which I just roll my eyes. Well fast forward to New year's eve she's complaining about Sarah again and finally asks my advice. I tell her exactly how I feel about Sarah and that I have no idea why she is friends with her. She agrees and says she's going to distance herself, that she just can't do it anymore. I check Facebook new year's day and she's thanking Sarah for having them over and what a wonderful time they had... 🙄 I ignore it. Well today she's telling me about how she helped Sarah have a yard sale over the weekend and how Sarah's dad is having health issues. I check Facebook and she's asking if everyone could please pray for her BEST Friend's dad. 🙄🙄 all the complaining she does and now Sarah is her best friend? Ok. I know it may be petty and stupid but that just really irked me and felt like a slap in the face. I'm honestly done listening to her complain and have decided to take a step back from her. How would you feel if you were in my position? Am I overreacting? Should I say something to her? I am just so annoyed.