The only thing I see when watching the play at full speed and putting myself in the position of only having one look at it in real time, is that the runner initiated her slide for the plate earlier than normal due to the positioning of the catcher without the ball or in the act of catching the ball. That would qualify as being impeded.
I was going to make this point as well, the runner left her feet before the ball got there. However, making an aggressive slide in anticipation of a close play is just good baserunning. I would consider the proximity of the ball at this point to render this to be in the "act of catching." Certainly a close call, but nothing to hang the ump out to dry for.