The "perhaps" relates, perhaps, to Decoud. Note that even love is not enough to overcome Mrs Gould's solitude, be it the love of the general populace or the secret love of Monygham. In a section of the novel devoted to the supposedly redeeming power of love, it is a significant inclusion. One is tempted to read this line as saying that Mrs Gould is exactly "as solitary as" any other human being, i.e., utterly so.