Nor did she know just what situation she might find at the Waring-Gaunts'.

They would doubtless be surprised to see her.

They might not need her help at all.
She might be going upon a fool's errand, but all these suppositions and forebodings she brushed aside.

She was bent upon an errand of simple kindness and help.

If she found she was not needed she could return home and no harm done.
Receiving no response to her knock, she went quietly into the living room.