Best wishes Tim. The most difficult thing is finding out what someone can really be like when you thought that you knew them.
The odd thing here which you touch on is that she has broken the 2 month “silence” agreement and enagaged solicitors with an accusation without even talking to you. She’s either not thinking straight or there’s another influence behind it.
Given that behaviour, I think one further attempt by you to discuss the real reasons behind the behaviour then you do need the protetcion of a solicitor. It looks like you’ve taken all the burden for the last few years, about time that was recognised.
Good luck. You’re not on your own.