Hello and welcome to the forums!
I've moved your post to our significant others/family & friends forum, but with a pointer left in the original destination.
In the absence of her seeing a professional, there's little for anyone to draw any speculations on.
When you say she has OCD (I have OCD) can you elaborate on that? If it's simply perfectionism, it could be more akin to OCPD- Obsessive Compulsive Personality Disorder is rather a different animal than OCD. OCPD is more 'thing have to be done the way I say'- OCPDers can be hard-to-live-with perfectionists.
It's also my impression OCPD makes for an argumentative person.
But really it's hard to say. A couple things might be to look over some of the disorder forums here. OCD will be challenging, as that forum is so full of people with sexual obsessions/fears. But if you dig enough you'll get some glimpse of other common OCD themes- also all OCD is OCD (despite some commonly used acronyms to distinguish some common sexual OCD themes) so it all behaves roughly the same- maybe you can glean some insight there.
As well as look over the OCDP forum- a much quieter forum, because a lot of people with OCPD refuse to acknowledge they're the ones with the problem. When something gets to the level of a personality disorder, some personality disorders (PDs) seem to be awfully difficult for the person to be self-aware enough to actually post here themselves about it.
And the other PDs as well- keeping in mind as you look at them- and I don't have scientific evidence for this (such as published works I can point to) but keep in mind that PDs are well, facets of personality gone wrong- if you want to look under a microscope, we all do things that might be Narcissistic, or Borderline, etc. it's when it's something that impairs your life and becomes a major part of your personality, I think, when it becomes a problem. So... if you see some traits in this PD or that, with your mom, remember that it doesn't mean she has that- that's why it'd be so much better if she'd see a professional.
Also some websites have mental health quizzes- it might be good to peruse around here and see if you can get a feel for what might be her issue, then take some self-tests inserting your unbiased opinion of her behavior, into it and see what it says. When looking for some self-tests, try to find ones from mental health websites and the longer the test, the more accurate it's liable to be. You can't decide 'oh so and so has _____ from a test that had ten whole questions, you know?
Keeping in mind also, that any testing not administered/interpreted by a professional, should be taken with a grain of salt (the shorter the test, the more salt needed, in my opinion).
If you want something that professionals use....
https://www.psychiatry.org/File%20Libra ... -Adult.pdfmight be a decent start. I'm not in therapy (yet, I'm not dead yet give me time) but if I ever see a professional, I have one of these already filled out to hand to them. Also I scored it myself and it sort of didn't really tell me anything I didn't already know about myself, but it seemed pretty accurate. It doesn't say outright 'oh you have this, or that'- it's meant to be interpreted by a professional who can use it as one diagnostic tool- but still you can then compare it to the traits of different disorders and see if it sort of gives you an idea.