Welcome to the forum. Bed sores should be dealt with properly. Since the bed sores are on the buttocks, you should be careful that the buttock area is dry. Moisture and urine which is acidic in nature may worsen the condition. Be cautious not to drag but to lift her whenever required.
You have not mentioned if she is diabetic, however help her control the sugar levels. Do not leave her seated for a long time at one position. Give her a nurse or help who will help her change positions frequently.
You can get her dressing done 2-3 times a day with soframycin
oitment or get the affordable bandages done to help her stay comfortable. Take care.