How can I get rid of someone's power of attorney status? 2 Answers as of January 12, 2012

My aunt has Power of Attorney over my moms affairs as she is in assisted living living with Dementia. I used to help mom when she was not ill with her properties such as being there when she could not because of an appointment or feeling badly , or she just could not be reached. My aunt is and always has had to be in control and have the upper hand. The whole family knew it but now it ha gotten worse since my mom is the only one of hers left other than kids etc. She is in her late 70s. My moms tenants have been calling me to help in some incidences. They either can't get a hold of her or when they do she is very rude. She always says mom has plenty of money but in same sentence says she will sell mom house and I can have what left. I have volunteered my help several times, because as she says she is tired of driving back and forth and to much stress. She also has had my cousin, his son and grandchildren living there pretty much rent free since no one works. Please help I don't know what to do. I would like to take it all away from her. If she passes then who gets control? I am 59. The power was not given to me at the time it was done because I was on a different path but that was 20 years ago.