She could not tell.

Her nerves now were somewhat unstrung, and the tears that always came so readily to her eyes flowed quite unchecked.

She could not very well move, for he held her knees imprisoned in his arms, but she was quite content to remain like this, and to yield her hands to him so that he might cover them with kisses.
Indeed, she did not know at what precise moment love for him had been born in her heart.

Last night, perhaps...

she could not say ...