The best way to change a person is to become an
embodiment of what you want him or her to adopt. You can become a great source
of reforming the attitudes of your mother or mother-in-law by setting an
example yourself in dealing with servants. This I think can prove most
effective. But you will have to be very patient. People take time to change.
Always keep in mind that your duty is to persist with what is right and to
leave the rest to Allah.
The other thing you can do is to console and sympathize
with servants whenever an incident takes place which hurts their feelings.
Affection and sweet words do help.