Age
Since her eldest daughter is 27, Lady Lucas must be at least in her early 40's. Given that she acts of an age with Mrs. Bennet, she may not be much older.
Family and Situation
Lady Lucas is married to Sir William Lucas and is the mother of Charlotte Lucas, Maria Lucas and at least one other son. It is likely that Sir William was merely a Meryton tradesman when she first married him and that the elevation to knighthood afforded a significant change in her lifestyle.
We are not given much insight into the Lucas family life, but we do see Charlotte cajoling the entertainers into performing at the party at Lucas Lodge suggesting that her mother may not fully be up to the task of keeping a gentleman’s household. Mrs. Bennet later implies that the Lucas girls take on some responsibilities in the kitchen so it may be that the family's background in trade affects how the household runs in a number of ways.
Appearance
We are never given any information about Lady Lucas’s appearance, though we do know her husband is fashionable and her eldest daughter is plain.
Character
The narrator tells us that “Lady Lucas was a very good kind of woman, not too clever to be a valuable neighbour to Mrs. Bennet,” who is consistently comparing the achievement of herself and her family to the Lucases, suggesting a longstanding rivalry. Mrs. Bennet does say “If [Charlotte] is half as sharp as her mother, she is saving enough,” suggesting that Lady Lucas is a shrewd housekeeper. Due to her friendship with Mrs. Bennet and the fact that a great quantity of Meryton news seems to reach Lady Catherine after Charlotte’s marriage, it’s likely that that Lady Lucas is a bit of a gossip.
