She flubbed a line. That happens to the best of us.
Now, if we want to talk about weird body language and such we could hold up Psaki as a case study. Tie her right arm behind her back and the woman can't talk.
She's just not comfortable in public speaking. She gets nervous and over-compensates in this manner.
I was in toastmasters and saw this a lot with new speakers and with some who just aren't comfortable in front of others.
I do think she realizes she's in over her head and the nervousness from that causes her to over compensate when speaking.