I think she already broke it! Bad Blood views count was at 7-7.5 million at this stage (16 hours), and its final number was 20.1 million, so I think Adele's final number will be around 24-24.5 million.
Youtube has incorporated a new system that allows it to be "more accurate in real time" and they got rid of the 301+ update since then. However, they are still not really accurate in real time so she still has a huge chance of doing it!