In the minds of the British press and a lot of the American right (as well as just some garden variety American misogynists and/or racists), Meghan is the scheming bridezilla who ruined a wonderful fantasy kingdom we've all enjoyed from afar for years. That will always be the image some people have of her. For some it's fun to turn any young, happy and driven woman into a shrewish meme. If I needed to have that fix, well, I've already seen Heathers approximately 50 times.
I have no doubt she can be difficult, and I've found some of her and Harry's moves rash and tone deaf at times. But I can't blame young and frankly, very naive people in love for being rattled by the situation they found themselves thrust into and the unbelievable burden put upon them to suspend their lives together and subsume it into "the Firm". And the stories she and her husband have told about how they were treated both inside and outside of the family are just too heartbreaking to ignore, not just the big stuff like the tabloids making all sorts of animal jokes but the smaller, passive aggressive things like asking after Archie's pigmentation. That's all too real. A lot of people will recognize stuff like that from their own lives and remember it.