Do not complain about other people if you are as bad as they are. A proverb. Mary says that Betty is jealous, but Mary is more jealous herself. People who live in glass houses should not throw stones.
PEOPLE WHO LIVE IN GLASS HOUSES SHOULD NOT THROW STONES
Meaning of PEOPLE WHO LIVE IN GLASS HOUSES SHOULD NOT THROW STONES in English
American idioms English vocabulary. Английский словарь американских идиом. 2012