On the original play posted by sbplaya...
As long as the umpire judges that the path the fielder was taking to the ball was part of her legitimate attempt to field it (and that the ball was in the vicinity to be fielded), then the fielder is free to take any path she chooses.
On this one, maybe your runner just caught a bad break. She might have been TRYING to go around the fielder, but she just didn't go far enough. Runner interference can be accidental and the fielder's protection on a batted ball is nearly absolute.
I've had to explain this call to a coach before and the closest thing I can come up with is- sometimes that's just the way the cookie crumbles. Or, better yet for softball, the way the ball bounces. The game is filled with odd bounces and rotten breaks and this interference call is one of them.
I didn't see the college game you mentioned. Did the umpire's actually call interference, or did they not fall for F6's acting routine?
A fielder might purposely move into a runner to in an attempt to "draw" an interference call (sort of like a guard drawing a charging foul in basketball). But if the umpire judges the move to not have been a legitimate part of her efforts to field the ball, the contact can be ignored- or, possibly, even become an obstruction call against the defense!