the individual is a highly respected female rising star that is on the firms Human Capital Committee and an advocate of women in the workplace
This is not illegal in a sense that for example it is not a criminal matter with which the police would get involved. However, from an employment perspective it can be seen as a discriminatory comment because it is made on grounds of someone’s nationality, which makes it potential race discrimination. This is something which can be brought to the employer’s attention and they will then decide how to deal with it. For example you can do this informally, or if you think this is a serious issue then you can also follow the grievance procedure. The employer would then investigate the allegations and decide what the most appropriate action to take in the circumstances is. It could be disciplinary action against the person accused of making the comments.
In terms of you taking personal action against this person, it is not really recommended. All you can do is make a claim for race discrimination in the employment tribunal. However, the fees are quite high and the potential compensation would be rather low as this was just an isolated incident and also not aimed directly at you.
you are welcome