Eostre is wandering back and forth around the Basilisk Gate Barracks, being tasked with checking and reorgainizing the inventory, particularly the food supplies. She comments on this angrily if spoken with or while making another round between stacks and boxes. She does not want to be bothered until she finishes the task.
If it is higher level than the spell slot you used to Counterspell, you must make a check using your spellcasting ability[See Notes] to prevent it. The check's difficulty is equal to 10 plus the level of the spell you are trying to counter.