If it turns out she was physically threatened, oh damn. That’s deep doodoo for POTUS.
I'm of the opinion that one of the reasons (one of the reasons, not the only one) that the investigation is going so slowly is that there's something undeniably momentous about charging a sitting president with high crimes and misdemeanors. If I were Mueller I'd certainly want my ducks in a row. The laundry list of shit they've been accused of completely swallows physical intimidation of a witness.
Coincidentally, that's one of the things that led to Nixon's downfall. Parallel to Watergate was the prosecution of Daniel Ellsberg for the Pentagon Papers leak. Ellsberg's trial was nullified (I think it was declared a mistrial, but don't quote me on that) after it was revealed that Nixon's goons had threatened to kill him repeatedly. Interestingly, Nixon's "plumbers" were convened to originally attack Ellsberg.