I think you didn't quite understand the point. In a constitutional monarchy like the United Kingdom (or, for that matter, all other modern kingdoms in Europe), the Royal Family is not responsible for government policy and must abstain from expressing opinions on political/partisan issues, which is the case here.
For example, it would be unthinkable and, indeed, perhaps even unconstitutional in the UK, for the Duchess of Sussex to campaiign publicly for a change in the law (as she is campaigning now for the ratification of the ERA in the US). The position most Britons would take is that, if she wanted to influence the legislative process, she should give up her royal status and stand as a candidate for member of Parliament. The Queen could, in private, express her opinion to the Prime Minister or other ministers on proposed legislation, but such opinions are always confidential and, in any case, once the government has made a decision on its legislative agenda, the Queen must accept it, except for most extreme circumstances. The last monarch for example to veto a legislative bill in Britain was Queen Anne in 1708 and, even then, she did so on the advice of her ministers, and not on her personal decision.
My take in this case, however, is that the Meghan is acting not as the Duchess of Sussex and a representative of the British Crown, but rather as the US citizen Rachel Meghan Markle, which is a legitimate constitutional right that she enjoys in the United States. That would become clearer though if she stopped using her British royal title in the US and did her lobbying activities under her "civilian" name. In my opinion, that would be the right thing to do to eliminate any controversy.
In any case, what that signals to me is that Meghan is "burning bridges" and making any comeback to royal life in the UK an even more remote possibility than it already was.
