My sister is having our competent 90 y dad sign POA her a primary and me secondary. She was POA for our aunt who died a few years ago, I never saw a copy of will and she took all monies and sold the house for a tidy sum, stating “she deserved it all.” So I am burned and very cautious this time. Is there anything legally I can do to prevent this from happening again? I do have a copy of my dads will. FYI She is having the same lawyer draw up POA papers.
I would highly recommend that Dad use an "Elder Law Attorney" instead of a general Attorney. The Elder Law Attorneys specialize only in everything involved regarding Elders. They will even help if for some reason your Dad needs to use Medicaid [different from Medicare] to help pay for his care.
While there at the Law office, have the Attorney do a Medical Directive, this will give you and your sister a guideline on Dad's final health requests. Thus no bickering later about what Dad wants or needs health wise.
Personally I don't think anyone deserves all of or any of someone else's money or processions, it is a gift bestowed. So her choice of words would throw a red flag for me.
Have dad seek legal elder advise and talk openly about his wishes, I know it can be very hard but, hey none of us are getting out of here alive.
Good luck with your sister and I hope for all that dad remains competent.