Laurie, I'm sorry to hear of your struggles with the many changes surrounding your mother as she and you continue the difficult path of memory loss. Many of us who
have walked this path before you can attest to having dealt with the identical phases of cognitive decline that you listed in your question.
Behavior changes in dementia patients are the rule, not the exception. You didn't mention what form of dementia your mother was diagnosed as having, but all forms have phases. Your mother is in a phase of denial that she is dealing with as best she can, but doing so through anger and rationalization. Remember, you're "just her daughter," and she is not about to relinquish control of her life easily to you or anyone. Nor will she willingly accept your explanation of the "what, why and how"¦" of her illness.
There are several steps that you can take to help yourself and your mother deal with this phase of her progressive illness. First, it is not your job to tell your mother that she has dementia. That is her doctor's duty, and she may not like what he has to say, but she will be less likely to strike out verbally at him or her if the explanation is properly delivered. Make an appointment to see mom's neurologist, and prior to that actual meeting, meet with, talk to or write to the doctor and explain what you feel needs to be accomplished when mom comes to see him.
Once the doctor explains to your mother that she has a disease called dementia, the next time mom says there's nothing "wrong with her," and she will, you can "remind" her by saying, "Do you remember when Dr. Jones met with us, and he explained that you're healthy but starting to forget things?" Then let your mom respond and let off some of her frustration, which will hopefully be aimed at her condition, but not at you.
Not knowing your mother, there is also a possibility that she is absolutely aware that she's not the person she once was, and she's frightened, confused and choosing anger as her method of dealing with her frustration and fears. I suggest that you ask her neurologist about either a referral to a geriatric psychiatrist or psychologist, and possibly ask if there are any medications that s/he can prescribe for mom that will take the edge off her level of agitation. Your mother may actually be suffering from depression, and that must be addressed as part of her total treatment plan.
I too faced a great deal of anger when mom's source of independence, her driver's license and car were taken from her. The best way to handle that confrontation is to allow your mother to broach the subject, not you. Then you explain to her that the State was concerned for her safety and the safety of others on the road and determined that it was best that she no longer retain her license to drive. Be sure to say that you love her, and you wouldn't want anything to happen to her or anyone else on the busy and dangerous highways and roads. Tell her that you're happy to drive her wherever she needs or wants to go. Then give her a hug, and ask her if there's somewhere she'd like you to take her and arrange to do so when you have time.
There is some good news for you and your mother, but it comes with a price. Your mother is in a phase of her illness where her fear, anger, frustration, and possible depression are all close to the surface, and she is coping the only way she can at this time. Because dementia is a progressive disease, regardless of any medicines your mother receives to help her with her anger, time will take her further down the path of forgetfulness. That is the part of the disease that is the price she pays, and you will lose even more of her as that occurs. The benefit is that over time, virtually all of the issues that led to her anger and frustration will be part of what she forgets, and there comes a time when her behavior and reactions will be focused on other things that have far less to do with things that she perceives you have done to her.
As you noted in your comments, you no longer see your mother as "there." Unfortunately that is true and often continues to devolve to where she may no longer recognize loved ones, and finds her own personal solace and place somewhere in her own mind, perhaps as a young woman 40 or 50 years ago.
I wish there were words I could write that would indicate that you'll get your mother back the way she was, but her disease is unrelenting and will continue to take her away. Do your best to make the most of every day. While she still responds to you, show and tell her how much you love her, and do the best you can to make every day for her easier. You have a tough job, but there's a lot of support available for you as well. Like you, I continue to walk that same road with my own mother, so I wish you strength and patience as you continue your journey.