Being a girl on base I'm gonna take a "flier" here and go with softball - sure, girls play baseball....99% of the time if a girl is playing a bat sport it's softball. If I'm wrong I'm wrong.
This may differ in other softball rule sets - NFHS, USSSA, NCAA, LL, Softball Canada, etc - but here is the official international softball rule:
Section 9: The runner is out:
m. When he interferes with a fielder attempting to field a fair-batted ball, regardless of whether the ball has first been touched by another fielder, including the pitcher, or intentionally interferes with a thrown ball.
Assuming the rule set still follows this rule sounds like they got it right.
While the force is on (the batter hit a fair ball and is now a runner), the runner on first is not safe on that bag. Once the batter is retired, the runner is now entitled to that base and is safe if standing on it.