I can edit the echo description to include the feeling in, basically the woman who fell in the echo was his sister and his only living blood relative at the time. In the series at that point, he had literally just stated how they were going to be fine, despite the fact they were in a home filled with fire and some nameless killer going around killing everyone to recreate the Tragedy of Sablier.

If that's enough explanation then I thought the parallel of his sister falling, who is the most important person to him and the fact it was Elliot's sister falling was similar enough to start the echo with the fact they were falling being the actual echo.