Dual violations on first of two FT's

[Tee]

8th grade girls game today, A1 shooting first of two Free throws, missed rim. At same? time B1 in lowest spot stepped into lane.

If B1 stepped first- no problem, award A1 another try on the first shot.

If B1 stepped in after the ball had missed rim- no problem- ignore it, and proceed to second free throw.

Obviously the problem is if they happen at same time, as appearently happened. I say appearently, because as trail, I was not looking at B1 in low spot.

If this were the second of 2 shots or a 1 and 1, then AP?