Base Running Rules: Can a Runner Be Called Out for Rounding 2nd with a Runner on 3rd?

Question
hello had a girl advance to first on base on balls pitcher not paying attention so she stole 2nd she rounded 2nd came to a stop and went back to 2nd. had a runner on third umpire called her out said that she could not round 2nd BC third base was already occupied? I can not find it in the rule book?

Answer
HI again SH,

You know, players should never give an umpire an opportunity to call an out, especially using the look-back rule.  With R1 stuck at 3rd where's R2 going to go without causing serious problems for her offense?  There was no need not to just stop at 2nd.

That being said it is legal for her to round the base (as long as she did not stop at 2nd), stop and immediately return to 2nd.  

3rd being "occupied" has nothing to do with it.

Mark