Maybe this is just the introvert in me thinking this, but I'd probably run - but to my room or somewhere private at home, rather than run far away. I understand why she probably wouldn't have been quite ready to explain herself then and there, but maybe having the opportunity to speak to someone trustworthy in private would have been helpful.

My other worry would be trying to control the power before it causes too much trouble, and I think Elsa would have had more success in that area had she been in a calmer mindset at the time. Obviously, in a sudden situation like that of course you're going to panic and it's no wonder she just fled instantly, but if you are able to keep a level head for a second then you might be able to take some control back before things get completely out of hand.

It's an interesting question though! Not something non-fictional people really go through, so it's a fun challenge trying to empathise with something like this. :)