She should close the sash, turn up the fans (if possible) and take a step back. Thankfully, this sort of lab accident is exactly what fume cupboards were designed to protect from. If the reaction does not run down on its own, she may need to neutralise the leftover solution. The more important question is how this happened – is it a question of lab tidiness, distraction or being tired? In any of these cases it is important that changes are made to prevent a reoccurrence.
Charles Harrison is a safety adviser at a UK university