Hi Agatha, thanks for posting your question today.
Most issues related to bad breath and "scum" issues is from a dry mouth.
Dry mouth could be due to a reduced salivary flow causing the dryness of her mouth. Dryness of the mouth is called Xerostomia, and is common as we age. Biotene is the most prescribed medication for this problem and it is available over the counter at any drugstore. This is website for it: http://www.biotene.com/
Other OTC saliva substitutes include Moi-Stir, Optimoist, Mouthkote and Salivart.
Other causes of dry mouth could be medications used for anxiety, depression, allergies, hypertension, diabetes, etc. It could also be from an auto-immune disease called Sjogren”s Syndrome. Smoking and chewing tobacco can also irritate dry mouth. She can try using sugar free gums and candies to help with the dryness. If she continues to have problems with dry mouth syndrome I would schedule an appointment with her physician for a blood test to rule out any auto immune problem.
The morning is the most obvious time for this to develop do to a long period of dryness which is why it is so evident in the morning. Hope this helps her with her problem. If you need more information about this issue please do not hesitate to ask. Please leave a positive rating because that is how I get credit for responding. Thanks.