Your search for "Bess as mother and grandmother: letters featuring Bess's children and grandchildren" returned 7 letters.
Bess (Lady St. Loe) writes to her servant Francis Whitfield with instructions for the battlement at Chatsworth. A postscript asks him to 'tell Bess Knolles and Frank that I say if they play their virginals that they are good girls'.
George, sixth earl of Shrewsbury, writes to his wife, Bess (countess of Shrewsbury), regarding the Peak's men's 'clamorous speeches' and a potential meeting with them. On a second page, he writes 'I write this because you may send my letter to them to see how little I account of their complaints'. In a postscript to the latter section, he explains that he will provide 'some place' for his son, Gilbert Talbot and the latter's wife, Mary (née Cavendish; Bess's daughter), but seeks Bess's advice in the matter. He also describes an episode in which Bess's son Charles Cavendish, along with some servants, went stealing out into the country at night, and asks her to advise him against such behaviour.
Gilbert Talbot writes to his stepmother and mother-in-law, Bess (countess of Shrewsbury), regarding the state of the Goodrich Castle estate and thanks her for the furniture she has given to him and his wife, Mary (Bess's daughter). He also writes at length about various provisions of fabric.
Bess (countess of Shrewsbury) writes to her daughter Mary Talbot (née Cavendish), mentioning recent visitors, and asking Mary to send news that she and her husband, Gilbert Talbot, are well, 'else I shall not sleep quietly'. She reports that her grand-daughters Arbella (Stuart) and Mary (also Talbot) are both well.
Gilbert Talbot writes a long letter to his stepmother and mother-in-law, Bess (countess of Shrewsbury), relating various news, mostly to do with conversations between himself, his father (Bess's husband), George (sixth earl of Shrewsbury), and the earl of Rutland at Worksop. Rutland has invited Gilbert to come to see him in Newark, but Gilbert wonders whether Bess thinks the queen would approve, 'considering what speeches she used to me of him'. The letter is also signed by Gilbert's wife, Mary (née Cavendish; Bess's daughter).
Bess (dowager countess of Shrewsbury) writes to Sir Robert Cecil in reply to a letter written on behalf of her 'unnatural son, Henry Cavendish', craving pardon to withhold her support of him in relation to 'those matters lately objected against him' as he has dealt so poorly with her in the past.
Edward Talbot writes to his stepmother, Bess (dowager countess of Shrewsbury), chiefly regarding his stepbrother and brother-in-law, Henry Cavendish's disgraceful debts and words spoken by Henry's wife, Grace (née Talbot; Edward's sister), in private to Edward's servant, who thought such speeches 'should not have proceeded from her'.