Can a grandchild be Financial POA?

I have a question concerning a grandchild assuming financial power of attorney, and am wondering if it's worth the time/hassle/family strive.

I posted about 10 months ago concerning my grandmother's care and my mother's emotional and financial enmeshment. You all provided me valuable advice, so I'm turning to you again. My aunt (absent for decades and never involved in actually providing daily care for grandmother) wanted to be financial power of attorney, and had my grandmother declared mentally incompetent. She then threatened my mother with having her investigated for elder financial abuse unless my mother forged the financial power of attorney signature of my legally incompetent grandmother. My mom did it. My Aunt has liquidated my grandmother's small estate, selling her home without even putting it on the market, and given away any possessions my family wasn't willing to purchase, to Goodwill.

I have just learned that my grandmother's AARP supplement that is required for hospice care hasn't been paid by my aunt since September, and the nursing home can kick her out. She no longer has a home to live in! My aunt and mother are a toxic combination, each making horrible financial decisions. I want to ensure my grandmother's care. How difficult would it be to challenge this forged financial POA in court, as a grand daughter? Is it worth it? How will my family take care of her without the help of hospice or access to a nursing home???? My mother was her daily caregiver for 8 years before she went to the nursing home last year.