UmpireErnie wroteBetween home and 1B there is no safe place for BR to retreat to. She can't go back and stand on home plate to avoid being put out. 😃
Which is why, in baseball, a BR who retreats (legally, I might add) back toward home to avoid the tag is ruled out when he reaches the plate.
I also agree with others that I find no logical basis for ruling Interference on this play. For whatever reason, softball sanctioning bodies feel this situation is a special case that doesn't apply between any other bases. Fine. But rather than ruling it Interference, why not just rule it similar to a three-foot violation, call the BR out, and leave the ball Live to make plays on other runners? If this is really Interference, then all similar acts (e.g., the aforementioned three-foot violation) should be treated as Interference as well.