Single word for (shrugging) hands action
Solution 1:
You can say that she threw up her hands.
throw up one's hands Raise both hands in the air as an indication of one's exasperation. ‘Dickens threw up his hands in impatience’ - ODO
Solution 2:
I think you could describe it as she splayed her hands, as in
“What's the matter, Nick?”1 She blew out her breath, splayed her hands in front of her. She took a step closer to him and said, “I know what's going. I know." (Catherine Coulter, The Eleventh Hour, 2002)
She splayed her hands in exasperation. “What are you talking about?" (Michael A. Martin, Fallen Gods, 2012)
Quinn shrugged his shoulder and splayed his hands, “I guess that came out wrong." (Robin Wood, Murder She Spoke, 2014)
Of course splaying is just spreading, so one can splay one's hands on something, etc., which changes the meaning of the phrase, but without such specificity I picture a gesture something like this.
1 Incidentally, I'm sure it's a spurious correlation, but the name Nick and variations thereof co-occurred with this phrase in my search results to a startling degree.
Solution 3:
I delved into the good old classics a little and could find some interesting formulae:
- "I have never entered on it," said Mrs Cadwallader, opening her hands. (Elliot);
- "There, again!" said I, stopping before Herbert, with my open hands held out, as if they contained the desperation of the case. (Dickens);
- "Ah, so do I, George," the old lady returns, shaking her head and parting her folded hands. (Dickens);
- So we just sit here flapping away helplessly. (from "Polisse" movie).
I also stumbled across "to do big arms", but it's to your judgement whether to implement this phrase as an equivalent to "What now?"/"I don't know what to do".