Here's my take on it.
She clearly doesn't like being constrained in any way. She has a lot to say on issues she's passionate about (which seems to mainly be being a woman and being a woman of colour) and wants to come and go and do as she pleases, exactly as she did before, but hasn't been allowed to. Even if you thought you knew what you were getting into, you probably didn't really. Add in having to move to a new country and becoming a member of a family not exactly known for their warmth and fuzziness, together with the ongoing onslaught of the press every day, I don't doubt it's been tough for her.
But I suspect Harry may be somewhat to blame. I think he promised her that they were going to make waves, do things a new way, she'd be allowed to say what she wanted to and that the RF would be welcome all this change but they have found themselves squashed and suppressed at every turn.
Also, from everything I've read, whilst he loves some of what he does - meeting people (which he clearly has an infinity for) the Invictus Games and his work in Africa for example - he was bored of the more formal, mundane stuff that the Royals have to do. I accept that he's incredibly privileged but it must be very difficult not having a defined role in life and not really being able to go out and find yourself one either. Charles for example - imagine waiting 70+ years to start the job you were born to do? The rest of us are retired by that point! That's why he's worked incredibly hard to make something of The Prince of Wales. Harry was apparently happiest in the army, just being one of the lads, being normal. I think Meghan has zoned in on that unhappiness and chipped away at him and this is the result.
I do feel sad because I really wanted them to suceed - despite being a bitter old cynic, I am also a hopeless romantic. But the more I learned about her, I just see her as ruthless. An absolute ruthless social climber. Whilst I don't blame her entirely, it can't be a co-incidence that he has effectively abdicated less than two years after marrying her?
Yes, he had behaved terribly and petulantly recently especially the lack of respect he has shown the Queen, his boss and his grandmother, by jumping the gun and releasing that statement effectively forcing her hand - he knows the game well enough to know that was never going to go down well - but I strongly suspect Meghan was behind that. But I do think he'll be back in the fold and hopefully he'll be able to build bridges with William & Kate once the inevitable divorce comes though. I hope so anyway because I think he's really going to need his family.