I have court appointed TEMPORARY guardianship (due to dementia and have doctors affidavit that she needs care for her activities of daily living) and go to court next month for hopefully permanent guardianship. I have also paid for a surety bond per directions of the court. Bank will only allow me to put a flag on her accounts until permanent guardianship is approved.
Dad was very angry when he first entered the MC and lost access to his money, but he actually adjusted in just a few weeks. Then we went through a time where he was concerned the money would run out and he would have to leave the MC. After I assured him there were enough funds for him to live there at least a decade, I only heard about his money again when he wanted to buy some collectible and couldn't.
As guardian, you are responsible for how ALL your mother's money is spent. If the court (in it's annual review) doesn't approve the money your mother is giving to your brother, you can be liable for those funds and lose guardianship. I encourage you to pull your mother's direct access to funds and strongly consider reporting your brother to APS to avoid that outcome. The court may overlook problems during the period of guardianship transition but you need to have responded and solved the problem when it came to your attention.
Did your mother contest your guardianship application? Is there any friction between you and her about it?
If you have guardianship then you have legal right to intervene and the responsibly to protect your mom's well being and that includes her finances.
Good luck, you will need it!
The sooner you can get the judge to see the reality of the situation, the better. For us, this turned into a nightmare. Even though my mom had drawn up a trust prior to the dementia setting in, and I was stated as the successor trustee, we still ended up going back and forth with the courts for over a year and a half, and spending $70,000 of my mom's money just to get back to the same thing she had spelled out in the trust years before - that if she should lose control of her faculties, I would continue as her DPOA and become successor trustee. Between my brother and a sister (who hadn't visited my mom in a decade, but popped back in to ally herself with my brother and stir the pot) they kept things chaotic and caused the judge to feel she had to prove that she was proceeding cautiously and "protecting my mother's rights", even though no one could ever validate anything they alleged (that I was controlling, seeking to profit from my mom, perhaps already had funneled some of her money to myself).
I don't advise ANYONE to get involved with the courts if they can avoid it, but you're already there, so get your attorney to convince the judge ASAP that your mom needs protection due to her own inability to protect herself.
Take away her debit & credit cards asap. Keep records of bank statements too.
Goo Luck!