My 65year old mother got home she yelled and was nasty had anger? later she didnt remember anything of it. what does this mean? she always is agitated

She may be very ill: if this is quite unusual behavior for her, and she doesn't have a psychiatric diagnosis it could be a sign of a stroke or another abnormal brain process. Encourage her to seek help, please.

Depends: this could be many different causes from depression leading to irritability to a neurodegenerative disease like frontotemporal dementia (Pick's disease) to a temporal lobe seizure disorder among others. she needs a thorough neuro evaluation with an MRI brain and an EEG if she there is no depression or prior psychiatric issues with anger