To think MiL is in the wrong here?

[TwoM]

DH has just been diagnosed with Asperger Syndrome. His mother was not keen on contributing to the assessment but eventually she did (made many excuses to delay it). She's made it really clear that he doesn't have autism and that she would know if he had that. I explained to her that there are different types of autism which manifest very differently, and Asperger is high functioning, therefore diagnosis is very difficult. It's been really tough for our marital relationship and life in general, and the last thing I or DH needs is someone close to him denying his diagnosed condition. She is one of those people who thinks she knows it all, dead stubborn and was even in denial when our DS had food allergies. I feel like having a harsh word with MiL because it's affecting DH badly and this is the last thing we need noe. Is she in the wrong or should I give her more time? She's known about him potentially having Aspergers for 3 months now, and I have been thinking about it to myself for about a year.

Thanks everyone, some very wise advice here. I think it's best I leave trying to convince her of anything. If she shows interest, I'll share, otherwise I'll leave her to it.

The naming is partly the problem. If assessors used the term Aspergers then MiL may have been more likely to contemplate it. But the moment you mention autism, it's like no no no, it can't be that, I would have seen the signs, I'm his mum (As classic autism is very different). And yes Aspergers the term wasn't used. I've just got used to referring to it as that.

High functioning just means no intellectual difficulties, not that the person can necessarily function well. Some can but it is bloody hard work.

Another thing about autism - it's relatively recent that it's been acknowledged widely as genetic. For most of your MIL's life, the main message spread was it was due to problems in mothering

That’s what I was thinking too. The “cold parenting” theory of what causes autism has been debunked but if it was around when your MIL was younger she might worry about it.
Also, I think it must be really difficult to hear that your adult child has something like this, because you probably start to worry should you have spotted it sooner, could you have helped him more, are you a terrible mother for not noticing etc etc. I don’t think it would be totally surprising if she was in denial.
And then finally I think there’s the issue of how most people without any direct experience can view autism. Often on tv etc it is only the more extreme end of the spectrum that it shown, so if she doesn’t totally understand it, it must be hard to reconcile her view of her (as you’ve said) high functioning son, with the image she has of autism being something totally different.
If what she is doing is upsetting your husband she does need to stop. But I think giving her time to understand that the diagnosis doesn’t change anything about who her son is, it just explains more about him and importantly can help give him tools and support to deal with anything he finds difficult is important.