Sometimes depression or certain illnesses cause a loss of appetite. Ask her medical team for advice. She is in a care facility and surrounded by the experts who should know her problems. They are the ones to treat her. I would arrange to have a conference with them to understand what is happening.
Suggestions for Less Severe Cases of Elderly in Family Care
Supply them with healthful food that they request. Try to keep a variety of healthful food that they will eat. Make the food tasty without going against their dietary plan. If they insist on oil in their vegetables, ask their doctor about Extra-Virgin Olive Oil. If it can be used, let them see you add the recommended amount in their vegetables. Brush their teeth, gums, and tongue regularly with a soft brush; and keep dental and other medical appointments. Sometimes sore gums or toothaches could be the problem that may not be known when the elderly person cannot communicate well. Look for mouth ulcers and tender gums. Bacteria and food buildup may cover taste buds and prevent tasting food. We usually do not eat what we cannot taste. Keep lips moisturized to prevent dry, cracked lips that could sting while eating. Look for signs of sore throat, constipation, or diarrhea. Keep them hydrated, and, occasionally, add a little real lemon juice or honey to their water to help awaken their taste buds. When possible, ask them about their well-being, and listen to what they may not say. Sometimes, the elderly may feel that they are a burden to others and may hide their problems. Make them feel comfortable and loved by exercising patience and good, personal care.
All of these problems and more could hinder a good appetite.