Timeline. Lead up to Kates alert indicating that Madeleine had disappeared.

[pegasus]

... when a child is apparently abducted, taken out a window, the parent doesn't run the opposite way and leave another two toddlers to their fate. A parent will always follow ...

That is exactly what she thought had happened.
She did look out the window.
Now, you are saying she should have gone off and searched alone, without telling the others?
Which way do you think she should have gone?
West towards Rua 1 Maio, or east towards Millennium?
How long do you think she should have searched alone, before getting help from the others?
Half an hour? One hour?
IMO the optimum decision was to go get help, it took a very small amount of time to do, and it meant there were multiple searchers, who could simultaneously check several directions.
It was a sensible decision by her, to get help, IMO.

[John]

Looking out the window into the darkness was hopeless.  Any parent in such a situation would have at the very least gone out the front door to check.

[jassi]

Looking out the window into the darkness was hopeless.  Any parent in such a situation would have at the very least gone out the front door to check.

Unless it was locked and she didn't have the key.

[peter claridge]

That is exactly what she thought had happened.
She did look out the window.
Now, you are saying she should have gone off and searched alone, without telling the others?
Which way do you think she should have gone?
West towards Rua 1 Maio, or east towards Millennium?
How long do you think she should have searched alone, before getting help from the others?
Half an hour? One hour?
IMO the optimum decision was to go get help, it took a very small amount of time to do, and it meant there were multiple searchers, who could simultaneously check several directions.
It was a sensible decision by her, to get help, IMO.

The search should have started from the table, well in the real world it would have.