When a person can no longer manage their own financial affairs, these will be managed either by their attorney (if a power of attorney has been made) or by their deputy if an application has been made via the Court of Protection in the absence of a power of attorney.
Once the appointment of attorney or deputy has been made, their responsibility is to act in the best interests of the person whose finances are being managed.
This is a strict burden and there are numerous instances of attorneys and deputies being hauled over the coals for inappropriate actions.
One of the biggest problems is that of making gifts. The person whose affairs are being managed may want to make gifts, or may traditionally have made them, and this can create a conundrum for the attorney or deputy as to whether gifts should be made and, if so, at what level.
Fortunately, the Office of the Public Guardian has issued a booklet called 'Giving gifts for someone else', which provides guidance in such circumstances.
The basic rule is that if the person for whom you act has mental capacity, they must decide whether to make a gift or not. Mental capacity is subject to quite strict legal tests and guidance is provided regarding these.