Sister-in-law accused me of faking my wife's diagnosis

Yesterday, as I posted elsewhere, my wife was diagnosed with ADD overlapping with Asperger's and OCD.

Today, my wife took the initiative to email her close blood relatives, her close friends and my close blood relatives about her diagnosis. She asked me for my opinion on her email before she sent it, so I suggested a few edits. I also said, "While I support you in this, I expect some of your relatives will probably react badly." My in-laws have scapegoated me for nigh on 20 years now, to the point where I decided to have little contact with them, so I'm well-experienced in how intrusive and abusive their behaviour can be.

Sadly, I wasn't wrong. I'm grateful that almost all my wife's relatives who received her email replied supportively - with surprise and questions, but supportively.

One of my sisters-in-law (a professional in her mid-40s), however, replied to everyone who received my wife's email (except my blood relatives) that my wife couldn't be suffering a mental disorder and that I had written the email and forced my wife to send it and that none of it was true. When my wife replied to correct her, SIL upped the ante and accused me of narcissism and of battering my wife.

That my SIL disapproves of me and my marriage and spreads vicious rumours about me came as no surprise to me after almost two decades of the stuff. What did surprise me was the strength and severity of her denial of my wife's diagnosis. I was expecting a similar reaction from their mother, a partly-treated bipolar disorder sufferer who at each birthday which ends in a 0 has gotten her son to write and read aloud to the assembled party guests a speech about what a perfect mother she is. MIL is on holiday right now and isn't expected to read her email until she returns in just over a week, so it could still happen. As is, SIL has threatened to delete the current round of emails from MIL's account before MIL returns.

I understand denial. I've been seeing enough of it in my in-laws for almost a couple of decades now: as long as they're burying me in hatred they don't have to stop and look at their own problems. I feel for SIL that she's too anxious to accept my wife's diagnosis just yet. I'm just not going to take any rubbish from her about it.

I emailed her and all those whom she emailed and said, calmly and politely, words to the effect of, "Allegations like these cause problems, not just for me, so if you ever want to hear my side of things just email me; and whether you approve or not, my wife and I will endure." I'm not expecting to hear anything from it except perhaps more vicious comments, which I will delete from my own account; nor do I expect any change in my in-laws' behaviour. I feel better, though, having stood up for myself to my wife's family yet again.

May you all have better luck.