Small decay under a crown/at the margin. Treatment options?

My dentist recently replaced an old crown. In between two visits (when she took impressions and put the permanent crown) I got pregnant. When she put the permanent crown she mentioned a small decay at the margin and said she would clean it when it's ok to use anasthesia. She said she would be able to reach it from underneath the permanent crown. Is it a reasonable treatment plan? I am worried that the permanent crown will be compromised or the decay will not be completely cleaned. Thank you!