Hello ConfusedHusband. Sorry you find yourself here.
I can relate to this post a lot. For me, that time felt almost like being in a loud room and trying to negotiate. Some of the words were getting through but I couldn't follow the conversation. Surely there must be a coherent rhythm to it and I simply am not able to follow it. I tried to work harder to understand, to read her lips, to estimate the likely next word. At least in my case, there was no misunderstanding. There were simply a collection of statements that didn't mesh with the actions I was seeing. It took me an incredibly long time to accept that.
I'll try to answer your questions but I'm afraid my responses may seem withholding.
Is this a MLC?
No one can know. MLC isn't a well-defined object with sharp contours and bold edges. It's a chaotic mess of symptoms and behaviors. From what you've described, it doesn't seem outside of the "norm" (for whatever that's worth). Regardless of any label we could attach, your wife's behavior is erratic and hurtful. She herself doesn't seem to have an endgame. It's good to see these clearly, with open eyes.
Are recurrences of a MLC normal which seems to have happened here (if it is one?)
Yes, there are a few stories in this forum of that happening. If we think of MLC as a style or family of coping mechanisms, then it seems reasonable that this behavior would repeat until the individual would deconstruct it as a response to various emotions.
How should I react? Should I push back on the office thing, or accept it in order to buy some time and provide her with time to get back to normal?
There is no RIGHT answer. The framing of "should" already has an implicit model that exists objectively "out there", if only one were sensitive or clever enough to sense it. There is no template or form or mold. There is no rulebook, or strategy guide. There aren't even any laws. Similarly, the future is unpredictable. There is another assumption that this is an aberration or mistake, and that, with time, things will "get back to normal". How do you know that? I don't ask that as a challenge, I ask it sincerely, genuinely.
Is the 'space' thing and office suggestion a way of her gradually wanting us to split up...or is it her wanting us not to split up by providing some distance?
It is impossible to know. I, personally, would be surprised if she herself knew.
All of this is to say, nothing is given or certain. Your partner is behaving in strange and unfamiliar ways. Your partner has explicitly called into doubt her belief in your relationship. Your partner has done nothing to repair or strengthen the relationship. She hasn't attempted to ally those doubts. Your partner does not appear to me to be reliable.
When I found myself in this position, I didn't want to truly believe it. Surely all of these other relationships had some kind of achilles heel, or fault. Surely these people don't understand the strength of our bond, the depth of our love. Surely this is a hiccup. Regardless of how I viewed my situation, the advice I received was helpful:
- detach
- focus on yourself and your well-being (and take your eyes off your partner)
- do more of what brings feelings of wholeness (i.e., do more of what you like)
- do less of what diminishes you (i.e., do less of what you don't like)
- surround yourself with people that love you (friends, family, support groups, therapist(s), etc)
- spend time in nature in whatever way you can
- sleep as good as you can
- eat as healthily as you can
- focus, as much as you are able, on the here and now
Half of this probably sounds incomprehensible (at least it did for me: "what the hell do detach and give-space ACTUALLY mean?

"), but eventually I came to some sort of internal understanding which made sense to me.
All of our situations our unique. If anything I wrote doesn't feel right, throw it out. Trust yourself. That's all you can do.
Again, sorry you find yourself here.