OK, this stinks. First of all, I never heard of any oxygen equipment that needs power, but I’m no expert, so we’ll assume that’s legit. If the equipment is portable and the power isn’t back on in 30 minutes, haul her azz to McDonalds or somewhere and plug it in. If not, get her in an ambulance, urgent care, hospital, etc. etc, etc. There’s only about 54 places in your town that have oxygen and electricity. Nice job. Granny’s in heaven now, slapping her forehead over having such stupid progeny (come to think of it, if she’s coherent, why didn’t SHE call 911?)
Likely not coherent. Under hospice care.