It really depends on what level you are umpiring.

If you see it and it is impacting on the play, then yes- pull it up.
TBH- the player is allowed to face her opposition, and you need to be clear that she is staring at her to intimidate.
Look at it a different way- what if the player is staring at her to gage which direction she will lead to, for the next pass?

Having not been there to see it myself, makes it hard.
Do you have a copy of the rule book?
Or 'U for umpiring'?
Every umpire should have one.