Avoiding INT
 

NCAA rules
I'm in "C", R1 on 3B, foul fly ball near 3B, R1, returning to 3B, tangles with F5, INT.

Later, coach says, "I understand why you had to call her out, but what am I supposed to teach them in that situation?"
I say, "standing on the base is the safe place to be; as long as she does nothing intentional while on the bag, she won't be called for INT"

PU comes up to me later to inform me that's not correct, she absolutely has to vacate the area so a fielder can field the ball. "If she wants to drop to the ground & keep a finger on the bag, that's fine, but she can't get in the way."

First time working with my partner, no sense in arguing (I didn't know the chapter & verse to quote him) so I let the conversation end there.

I'm new to NCAA. Does 12.6.2 apply here?

I believe this is the rule you want.

12.19.2.1.4.1.a When the defensive player, while watching the flight of a
ball, bumps a base runner who is standing on a base and fails to make a
catch on a catchable ball, the base runner shall not be called out unless
the hindrance is intentional. A base runner must vacate any space
needed by a fielder to make a play on a batted ball, unless the base
runner has contact with a legally occupied base when the hindrance
occurs. This is an exception to the rule that defensive players must be
given the opportunity to field the ball anywhere on the playing field
without being hindered.

Your partner is incorrect. I suggest you don't let it go. Forward the rule RKB noted to your partner and explain this was the basis for your ruling. You will be doing everyone, including your former partner a favor.