That's terrible that they treated your emotions with such disrespect. They really should have taken the time to speak more with you, and with the family. But it is, of course, great that she has another donor. Probably picked because of being an even better genetic match?
Keep in mind that donated kidneys do not last forever. Many do indeed last for decades, but others fail after a much shorter time. So she may in the future need a second transplant, and you could, if you wish, stay "in reserve" for that situation. Or (once your emotions have had time to heal) you might consider going ahead and donating to someone else?
Fr. Pat