My nan is forgetting that she’s been to the toilet

For the past few months my 83 year old nan has been complaining that she can’t go to the toilet. After visiting a doctor saying she can’t go they then gave her strong laxitives to solve the problem. After getting a bit suspicious of her saying she still hasn’t been in days. I’ve been trying to listen to when she’s going… she’s been going to the toilet about 4/5 times a day. She gets confused at night and then gets angry that she hasn’t been to the toilet all day? I’ve tried to explain to her that she’s already been 4 times and she just gets angry saying that I’m lying trying to make her look like she’s loosing her mind. PLEASE HELP. She is absolutely obsessed with emptying her bowel completely. She doesn’t want any food in her stomach because she thinks it’s going to get blocked. She’s never been tested for any dementia, but is this a symptom?

Dementia takes many forms.
If she is repeatedly forgetting, then that definitely needs to be flagged up to the GP.
How is her general health?
Who else lives in the house?
Is it her house?