(a) That's right. In cases where a general controlling influence is neither presumed nor proved to exist, it may still be possible for a person who wishes to avoid a transaction to prove that that they consented to the transaction because of the undue influence exercised on that particular occasion by a person with whom they have a relationship and in whom they have placed their confidence and trust.

Therefore, even though the facts suggest that A did not exercise a general controlling influence over B, it may still be possible for B to prove that A improperly exercised a controlling influence over her decision to transfer the house to him. The given facts are probably sufficient to establish this and the transaction would therefore be set aside as void.