I am so glad to see you online. This is not my expertise but my MIL is also very forgetful so I have been keeping an eye on her. Here are a few tips that may help you in deciding if you should keep encouraging your MIL to see her physician. My MIL is 85 years old but she has been forgetful for years so I just watch for changes.
Memory problems that aren't part of normal aging:
Forgetting things much more often than you used to
Forgetting how to do things you've done many times before
Trouble learning new things
Repeating phrases or stories in the same conversation
Trouble making choices or handling money
Not being able to keep track of what happens each day
Wishing you the best and I miss you !