Being thousands of miles away in California should should have made it easier, not harder, to avoid doing anything inappropriate or attention-grabbing. Kate at least had to sit through the ceremony and then walk back with cameras focused on her the entire time. All Meghan had to do was not issue a press release.
Obviously they didn't stop the funeral to announce "That wreath over there was sent by Meghan, done by the same florist she used for Archie's christening... " and then listed all the flowers. And I don't imagine any of the guests were aware of it at the time, since they all had better manners than to whip out their phones to check the media coverage. That doesn't change the fact that Meghan - who, as you said, wasn't even there - has managed make herself a centerpiece of media coverage of an event that had nothing to do with her, and that she didn't even attend. If that had happened without her doing anything because the media is obsessed with her, that wouldn't be her fault, and it wouldn't be fair to criticize her for it. But it didn't - it happened because she thought it appropriate to issue a press release (anonymously, for some reason) about her contribution to Philip's funeral while that funeral was happening.