How do I handle my girlfriend diagnosed with mild dementia?

One of the first signs of my LO's dementia was her being nasty, ill and generally disagreeable for no reason. I didn't know why at first. In retrospect, I saw the signs. All of the tips above are great suggestions. Learning what to expect should prepare you. Not that it's easier to deal with, but, at least you will know what's causing her to act that way.

Richard12345, take your girlfriend to her primary doctor and have her checked for an urinary tract infection [UTI] which has symptom that make dementia worse.  Hopefully it is the cause of her being nasty.  The test is very easy, and can be treated with antibiotics. UTI's are common as we age.

Also get a copy of "The 36-Hour Day".

Hi Richard,
You've come to the right place. The person who can help you understand your GF best is Teepa Snow. I've attached a link to her articles on this site. Also check YouTube videos by Teepa Snow.
Come back here often for support.

https://www.agingcare.com/search.aspx?searchterm=Teepa%20snow