the map isn't the territory
Pretty much judgement by the umpires, the ones i had i only seen one and ejected the young child sadly. However if i am with another Umpire we talk about it and if we both don't see anything. Its more of the momentum than anything else. Most girls seem to care and check on others.
One thing I've gathered from this, and something I've debated with umpires who don't know the rules, is that for contact to be "malicious" it just has to be "an act that involves excessive force with an opponent.” It does not have to be an intentional act meant to injure or anything. The base runner doesn't have to do her best Albert Belle impression. If she's just cluelessly running the bases and knocks a girl into next week because of her own ignorance or lack of athletic ability or whatever, it can be worthy of an ejection.
I am still super bitter about one of my players suffering a concussion because a girl on the other team wasn't taught to slide, and all the umpires said was "well, we called her out." Of course you did. Because she was tagged out before she trucked my player. grumblegrumble
As with many of refree articles, they are partially correct, partially wrong. Crashing into a fielder isn't just if they simply have possession, it is if they have possession and are waiting to make a tag. A runner cannot instantly stop or change course when a fielder suddenly received a throw 1/4 of a second before the runner got there.
Also, while NFHS does allow for a runner to be called out if the contact is rule malicious, USA softball has no such rule. And simply pushing a fielder is not necessarily interference. In USA, if the umpire judges the contact to be excessive they can eject for unsportsmanlike conduct, but they cannot call the runner out.