I recently discovered that the public guardian has been handling my mother's fiancial affairs. I am her son and i do not approve of this I have POA.

The public guardian can only handle your mother's finances if they obtained conservatorship of her estate. When they filed for the conservatorship, they would, by law, have sent a notice to your last known address, notifying you that they were filing and informing you of the date of the hearing. That was your opportunity to object. There should be an accounting every year. That will be another opportunity for you to review what they have been doing and file any appropriate objections. The conservatorship trumps your power of attorney.