I think my mom has Parkinson's/Lewy Body Dementia. I am concerned, but I don't want to scare her. Suggestions?

Important for you both to know. If parkinsons there are medications that can help. Mom must get to her doc for diagnosis.
My brother was diagnosed with probable early Lewy's Dementia solely by his symptoms. He was willing to discuss it. In fact he talked to me about his hallucinations at nighttime, asking what could cause them. Does your Mom mention hallucinations to you. What other symptoms does she have. I am willing to discuss my brother's specifics but usually have my private messaging closed. It is open today; if you can PM me before midnight I will be happy to elaborate. She may be more willing to discuss this with you than you think. My brother said, before is death, he was glad to know what was happening in his brain, why he was having episodes and the ways in which he was seeing the world differently. Not glad to know what would be the long slow slide were he to continue, but glad to know. Do know that Lewy's of all the dementias can present as better and worse, like a stock market chart, whereas other dementias are more solidly progressive downward.
Meanwhile, be certain to get all paperwork, wills, POA done now while Mom is able to agree and understand what she is doing. My brother made me Trustee of his trust and his POA so I could function for him as he failed more.

Tell mom it’s time for a check up with the doctor, you don’t need to be specific about why or you can make up some general reasons for the visit. Then you can either write or call the doctor before the appointment and outline your concerns. The doctor may not be able to talk to you because of privacy laws but you can talk to him/her. Any diagnosis or news is best coming from a professional and not you

I bet she knows "something" is wrong.
I bet that she has been covering up for years.
No important discussion is easy. Just like the one she had with you about sex. Ya just gotta take the dive and go for it.
Good possibility that while she may be defensive, argue that it's not true, I bet deep down she might be relieved that she does not have to cover for herself
What is important is that she realizes that there are decisions that she can make now that will make things so much easier for her and you and the rest of the family in the months, years to come.
End of the year.
New location, maybe a new doctor. Time to get a complete physical. That is maybe the best way to start.

Shouldnt have to do anything other than take her to her regular Dr's visit and let the Dr know of your concerns

I have found, both with my Mom and now my husband, is to send a letter to the Doctor prior to the visit or bring a letter with you to the Doctor visit and pass it onto the nurse with a small note to give it to the Doctor before seeing the patient. They have appreciated getting it in advance.

Do not even attempt talking about any condition you think she might have. First you might be wrong, second, she will become angry with you breaking off communication and working with her in future. It will cause her to be uncooperative with you and/or Doctor. Or she might refuse to go to a Doctor appointment or even let you go in with her.

I would calmly suggest it might be a good idea you go in with her for her upcoming Doctor visit, so you can ask and understand anything you should know in order to best know what is best for her, now and in the future. No mention to her about what you think she might have.

When my husband was first showing signs of Alzheimers forgetfulness, for some unknown reason I felt he had to admit he had a problem. Now that was not too smart on my part. If angered him and frustrated me. No win! When I stopped, it calmed things way down and I found him to be quite cooperative.

I now keep things going as if all is normal, including him, when it is by no means normal. But it helps keep things calm.

My mom has Parkinson’s disease. Please see a neurologist. She will be put on medication to help control the symptoms. Parkinson’s disease is a progressive disease and does not have a cure.

My mother had Lewy Body Dementia and there are a couple of things to bear in mind. One is that it is fairly quick to progress and unfortunately there isn't a drug that helps. Beware of anyone prescribing anipsychotics for agitation, as they make Lewy Body Dementia worse.
The other thing is that she may not have much self awareness of the illness. Or at least my mother didn't. It was not easy to get her to agree to an assessment.
Delusions and hallucinations are common. We found it hard to get a diagnosis until it was clear that my mother was having these. After an episode of delirium the diagnosis of LBD was made in hospital.
Good luck with everything. x

Just make the Dr appointment with Neurologist. Let the Dr access and determine diagnosis and treatment. No need to scare her. LBD is the 'roller coaster dementia.' Meaning both good and bad days will follow in her abilities but not complete down trend in abilities as tends to be the case with Alzheimer's. Take things one day at a time. Good luck to you both. Thank you for caring enough to get your mom the help she may need.

I went through the same thing with my mom. I decided to have the doctor (Movement Disorder Specialist) explain it to her at the next visit. Doctors do this better and do not emotional about it. Maybe take some questions with you that your mom can hear being answered. Hope this helps.

Thank you for all the reply's and advice! Since I posted, my mom has seen her Neurologist twice and is scheduled for a neuropsychology exam to determine what is going on. I didn't say anything to her prior to the appointments. I just wrote a list of my concerns and things that happened and gave them to her doctor for review. The doctor did say that she has some type of dementia going on. My mom disagreed, but then her doctor pointed out that her previous Neurologist had her taking dementia medication for the past several years. My mom didn't realize this (or forgot/blocked it out). She thought all her brain problems were from previous TBI's (last one was in 2019). I guess her previous doctor set her up for a neuropsychology exam several years ago, but she never went. She claimed doing so made her feel stupid and that's why she didn't go.

Now that I am helping her with her healthcare and working with her doctor, she has agreed to go. Hopefully, they can determine what type of dementia she has, so we can have a better understanding of what she is facing. I'm also curious to see where she's at with the disease. I know there isn't an exact way to determine this, but she is definitely not in the early stages. She has been having problems for many, many years.

It's stressful for all involved, but I'm glad that I can help her. Before she came to live with me, she was in denial about many things and hid a lot of things from her spouse, family, doctors and even herself. I do see her letting go of the denial a little bit at a time and accepting her situation. Maybe it's because she can't cover things up with me and make excuses anymore now that she lives in the room next to me? Maybe it's because she has my help with her healthcare and I know everything the doctors are saying? I'm just glad that things are changing for her and moving forward despite her diagnosis.