I can see that it might not be possible to give full details - but unfortunately that does mean that the request "what to do?" can only result in inappropriate answers, as the full facts are not available.
What does come across is that you do not like this DIL, which is why the "least said, soonest mended" advice is particularly relevant.
Unite the Kingdom and Pro Palestine marches Cup 16th May 2026
without knowing the full background and facts no-one could be expected to give a helpful answer.

