Legal play

[Lancerdad]

This question is from one of my Umpires that does softball games for the
league I assign for.

Today I had a walk with a runner on second. The runner on second stole third while the batter was walking to first.Now I'm not positive of where the ball was, but I know it did not get past the catcher, and I'm pretty sure it was about in the pitchers circle by the time the girl reached third safely. The coaches of course were asking about it, and I ended up sending her back to second. Was this the right move, because I've never came across it playing softball and it just didn't seem right...?

Thanks,
Brian in MI