If the mother-in-law thinks her daughter-in-law is too lazy, she can consider the following methods:

1. Respect each other: Respect your daughter-in-law under any circumstances, and don't hurt her with words or actions.

2. Communication: Communicate frankly with your daughter-in-law, let her know that you think she is lazy, and hope that she can participate in housework more actively.

3. Fair treatment: don't let your son do housework, while your daughter-in-law doesn't need to do it. You should distribute housework fairly.

4. Help: If the mother-in-law has time, she can help her daughter-in-law reduce the burden of housework.

5. Guidance: If your daughter-in-law doesn't know how to do housework, you can teach her how to do it and guide her to develop good habits.

No matter which way is adopted, to avoid conflicts, harmony should be the most important.