Baserunning question!

[Reffing Rev.]

Horrible field, no fence more than 6 feet up the line on either side, so we've got dead ball lines extending from the fence about 8 feet from the foul lines.

Runner on 1st Ball hit right field corner. Runner is booking around the bags and rounds 3rd about 9 feet wide (outside the dead ball line) I am trailing the batter into second with the throw. I had no idea this happened, but my partner ruled the runner out for leaving the playing area.

2 questions...
1. Is this a good call?
2. How much out of play would she have to be?

This is a SP league using a combination of ASA, NCAA, and MLB rules..