Judy, 54, said the Czech-born former world number one was "great fun to have around" and habitually called her "Granny".
She said Lendl gave her the nickname after she had her hair dyed silver. In fact, he is only six months younger than her.
But she said he had made the crucial difference in transforming her son from nearly man in to Wimbledon champion.
Judy said: "It's very sad and I'm still in mourning a little bit. I think we'll all really miss Mr Lendl - we used to call him Mr Lendl and he used to call me Granny.
"When my hair changed colour obviously I paid a lot of money for my hair to change colour. It didn't change colour from the stress of working with Mr Lendl."
She added: "Andy learned loads and loads from him and without doubt he made the difference of helping him to get over that final hurdle."
Murray and Lendl split by mutual consent after two-and-a-quarter years working together.