OP, if the organisation is a large one, say 500+, then there will be codes of conduct etc published & implemented by HR.
Today sounds horribly tough for you.
You needs to get advice for yourself (e.g. ACAS, trade union, employee assistance, independent solicitor) as you have your wellbeing, your health, your children, your job, your career & your marriage to consider.
Put your self first, get advice.
You must tell your line manager or HR so that an independent manager can be brought in to manage the situation. You do not find this person.
At her last 1:1 were the comments about a change of location for career development documented & signed off/electronically filed. If so, this may help the independent manager resolve the situation. It may be helpful for the organisation to activate her request for a career development move.
BUT, big but, bear in mind at this moment your knowledge of the relationship is hearsay. You have only your OH’s word that they have a relationship, the extent of it & that her OH knows. Please bear that in mind. How you get beyond that to actual confirmation &/or evidence so that your employer can resolve the management issue, I cannot say.
Other than professional contact, please do not discuss with her or influence the situation as the complexity of your line management relationship is sharply skewed by what your OH has told you. I doubt this, but he may have just made up a load of bollocks. Tread carefully & take advice.
I am sure you are incredibly busy but could you take a half hour out early this afternoon to ring employee assistance for emotional support - if your organisation has this service - &/or ACAS for employment advice where you can discuss your workplace situation without prejudice.
Acas Helpline - on 0300 123 1100.
I wish you all the best to get through today
.