Maybe the Police have had enough of her many years of brushes with the law that lead nowhere, and are finally throwing everything they have got at this.
All DV claims are taken very seriously, and it could even come out that she also attacked him that night too? Clearly they are protecting each other and the Police know that.
But ultimately, it comes down to strong evidence for a charge, that’s going to be the tricky part. In the Caroline Flack case, the place and her BF was covered in blood, so they had enough evidence there to take it to court regardless of her BF dropping the assault claim.