That's the one. There's a theory that onions help neutralise the effects of mace, they've been used by protesters in the Middle East for this and it's possible some of the Capitol rioters came with them and gave her one.

That sounds dubious to me. Have you chopped onions? What I’ve heard is that she probably wasn’t maced and was just using the onion to irritate her eyes and force tears to fake being maced. (People who actually get maced tend to be slobbery, snotty messes.)