In Mrs. Dalloway, does Clarissa host parties because of her innate desire to bring people together or simply because she's fulfilling her role as an upper-class lady?
Or does she host parties for another reason? Clarissa, who has been described (rather derisively by Peter?) as the "perfect hostess" does mention that she believes her parties are something of "gift", meant to bring people who live somewhat isolated lives, together.
The semi-ornate marriage of Richard and Clarissa Dalloway is quite representative of the social English traditions of their times; the demonstration of a productive and virtuous home, of a care-free lifestyle, and of a (even if falsely) loving family is the primary proof of a head of household who has done "well" for himself, especially after the turmoil of World War I.
In a way, we could say that, considering her social station, Mrs. Dalloway does not have much of a choice as far as to how to live her life. At fifty two years of age, she has lived through the peak of Victorianism; a time where women were seen and not heard. Moreover, the historical context of the novel occurs during a time where entertaining was the chief occupation of the upper-class lady.
Surely Clarissa was quite aware of that when she chose Richard as her husband, and there is little evidence to suggest that her entertainment was done in any way ill at-ease. We could safely conclude that the entertaining duties are second-nature to a character like Clarissa, and that this kind of activity is quite expected from a woman of her class.
However, the fact that Mrs. Dalloway is actually quite a retrospective and self-analytical character makes us wonder to what extent the superficial portrayal of her family makes her actually happy. After all, she is a woman who claims to want to find herself.
She had a perpetual sense, as she watched the taxi cabs, of being out, out, far out to sea and alone; she always had the feeling that it was very, very dangerous to live even one day.
Therefore, as you statement says, in a London society shaken from its foundations by the War, and now surrounded by the shell-shocked, the broken, and the scared, Mrs. Dalloway has come to the realization that the new world which surrounds her is quite alone. Alone, together. She sees how each of the people she knows has known pain and still try to move on. With a bit of a grudge, she realizes that she has been overly protected and, perhaps even way too lucky, to feel what the shaken have felt. She may even wish to be one of the people who were touched by a life-changing event, however, she realizes that her life is basically what will always be: a superficial show of cohesiveness.
Conclusively, Mrs. Dalloway she uses the medium of togetherness as a way to humanize an otherwise sad situation.