I read somewhere that apparently they broke up early November but they are still very good friends, hence why she was at the races (supposedly you can see him ignoring her a bit more post-race....I haven't looked so can't comment if this is the case)
Not sure if the 'good friends' thing is a cover-up or not but their families have known one another for a very long time and they have similar friend groups so this would make sense if they were friends still
Take it all with a pinch of salt though- have seen a tweet which was hinting at the fact that he cheated as well so it's possibly this break-up was not as clean as it seems to be at a surface level