I don’t really think it was a mistake since it is a really short video and who even uploads something without watching it back plus pulling the shirt on the end was also on purpose… I think she is just making a little bit of drama to boost views and make everyone excited for something similar to happen.
She also didn't like doing lens licking videos (I forgot her reason why) and stopped doing them for quite a while then she brought it back this year. And not only that but she's been doing lollipop licking and sucking videos as well when 2 years ago she was quick to remove a lollipop from her mouth and never show herself with one in a video ever again until now.
Another person commented and she said the same thing and a minute after her reply someone else said nip slip. I don't know why she's trying to cover up her image so cleanly. Just admit it was cause of nip slips. Why pretend like that wasn't the reason why. Just be honest with your audience. Unless she is afraid of the responds she gets back but I think most of her audience is understanding to not lash out at her because of it.