Behavior problems: If we don't know if dementia is causing the outbursts and acting out, do we ignore or point this problem out to her?

My 84 yr old mother is being tested now for dementia for symptoms of short term memory loss, lack of concentration, etc. I believe she might be in beginning stages of dementia so won't be surprised if the doctors tell me that. However, I'm confused about one problem area we have with her. She has always been impulsive & impatient. Lately, she's become increasingly rude to people, flying off the handle, cursing & telling people off & constantly interrupting people. One example: I took her to the bank & she didn't like what the teller told her that she needed to do. She started cursing & the teller was horrified. I told Mom to settle down & stop cursing. She at first denied cursing at the teller but then admitted it, was embarrassed & apologized. Another is a recent episode of her not being able to find an important document that she needed. I live many miles away so I was trying to tell her over the phone where it was. We had a few phone conversations for a week over this "missing" document & it came to a point where she needed to find it. I insisted she had it but she insisted she didn't. I convinced her to go to where I left her important documents & look again. She yelled at me that it wasn't there so I yelled back that she needs calm down & listen to me. I talked her thru it and she eventually found it. She immediately apologized to me for yelling at me (and of course, I apologized to her) so life went back to normal. She recently told me that she called the phone company one day for a tree branch on her phone line. She told me she cursed them & hung up on them. It was because they didn't give her the answer she wanted. I've calmly talked to her about her increased cursing in a private setting & her answer to me now is "That's just the way I talk". Before, she would deny cursing, but finally acknowledged it & said she can't help it after I repeatedly pointed out when she swore.

We had to put Dad in a long term care facility over a yr ago & Mom's world has been turned upside down because of it. Mom has had to learn how to pay bills, find people for household repairs, lawn care, etc; all the things Dad used to take care of. She hates being alone & has always been afraid of being alone at night. The behaviors that I'm seeing are a life long problem but have gotten to the point where I cringe when she recants her most recent episode of telling someone off. She can certainly remember telling someone off but cannot remember if she paid a bill or what the bill was for.

If it's dementia, do I ignore it when she acts out to others? If it's not dementia causing this problem, do I point it out or ignore it? I don't want to treat her like a child but I worry that she might be in a store one day & get mouthy someone who will not tolerate it. Dad never tolerated these behaviors & I've noticed that she does not act out when we visit him. I've been with her several months at a stretch since Dad got sick & life was fairly calm then. I took care of most matters, & kept her from getting mouthy publicly. She would go into tirades in private but I could usually get her to calm down & listen to logic. If I let it go, she'll harp on & on. Nit-picking is a personality change in her but I think that goes along with dementia. She's not done that to me yet but it might be that she knows I'll only tolerate it within reason. It seems to me that she knows when she's acting badly & can even control it in different surroundings. I also wonder if stress is the root cause.