That was my impression as well. I doubt Isabella is well acquinated with the castle. She only knew if she remained therein, she would be found.
Santuary was her only hope to escape the menace of Manfred.

Father Jerome informs Manfred that Isabella 'entreats your consent to remain in sancturary till she can learn news of her father; ' (ch. 2)

To speculate, this indicates it is Isabella's idea to reveal to Manfred her whereabouts and her intention, with the approbabtion of her guardins to dispose of herself in a suitable marriage.
Isabella is really telling Manfred to shove it !
She wants to get as far away from the lusty villain as possible.

Possibly, Father Jerome puts the words of a frightened girl into respectful terms for Manfred and Hippolita to hear.