Unfortunate, but in a sanctioned game, #3 can not be added.
She can be a sub, as a PH for example, if the coach wants here batting right then.
As far as already fielding in
all three innings, there was no appeal by the other team, so that stands. However, unless used as a sub, #3 can not field anymore.
Would anyone think the coach was trying to just pick the spot she was needed most to have her at bat?