My mum has been recently diagnosed with mild/moderate dementia and I feel everything is progressing quickly in the last few months. Her mobility is so bad and her speech is getting slower and more delayed. She sees and hears things that are not there like massive spiders or children in her flat that are not there. This is really causing her distress as she really believes they are there!
For instance, there are medications that are often prescribed for Alzheimer's patients that Lewy Body patients cannot take.
Also with Lewy Body, patterned textiles, wallpaper, and carpet can trigger hallucinations. They say it's better to switch to solid colored curtains, etc. to help calm things down.
Do you notice a time of day when things are more frightening for your mom? Sometimes patients get something called "Sundowner's" -- at dusk they get more disoriented and then more panicky and clingy. There are sometimes things you can do like changing her schedule a bit or putting lights on automatic timers to come on before dusk so there's not a dramatic change in lighting.
Hopefully other people will have more to say, but these are just a couple ideas. It is a hard road. I'm sorry your mom and you are experiencing this. She is lucky to have you looking out for her.
Do you have in-home help for her? Are you in the UK? There are a couple of people on this forum from there who might have more specific suggestions about resources there.
"If he has been standing at the window that long, he is probably deeply lost in thought, or daydreaming. He just didn't notice you waving at him. You know he has always been a friendly neighbor. ... I really feel like coloring now. Shall we get out the coloring box?"
"Why yes, that man did look remarkably like cousin Leon. I wish it was Leon! I haven't seen him since he moved to France. You are quite observant to notice that resemblance! After we find the lotion we are looking for, let's sit in the food court for some tea and maybe biscuits."
What she sees is her reality. If they aren't frightening or agitating her, try to respect that.
I know that other people deal with this by simply setting extra places.