Hi.. There is no bone loss, inflammation and soreness may be due to deposits present around the teeth. As your sister underwent scaling procedure from then she can maintain hygiene by brushing. Once hard deposits (tartar) are formed then again scaling is required. Main aim is to prevent tartar formation by regularly cleaning.
Next Steps
Correct brushing technique - see that all the surfaces of the teeth are getting cleaned. Rinsing mouth after eating anything helps in removing the food stuck between the teeth.
Health Tips
There is an impacted wisdom tooth in the lower left back region, that might cause trouble so better get it removed.