Who is Tishy Grendon in Henry James's The Awkward Age?

Tishy Grendon is one of Nanda's friends, a married woman whom Mrs. Brookenham strongly disapproves of. She believes Tishy to be a bad influence on her daughter for encouraging behavior she believes to be vulgar (though to a modern reader it would seem relatively tame), like reading romance novels. Tishy is generally looked down upon by others in the Brookenhams' social circle as well, including the Duchess (otherwise known as Mr. Brookenham's cousin Jane), who criticizes Mrs. Brookenham, her close friend, for allowing her daughter to associate with Tishy at all. Later in the novel, the whole cast pays a visit to Tishy's estate, and the simmering tensions between them all come to a boil, leaving the group in shambles.