I think that Anne feels very aged by her unfortunate love affair. Life essentially ended for her through her own actions -at least the pleasurable parts of it. As evidenced by her loss of bloom, no desire to dance, refusal of all other lovers, etc.

Cpt Benwick lost his love through no actions of his own - he has no blame in his loss and since his love is dead, he has no expectation of ever renewing his affair. Anne may think these factors will help him get over it faster. Anne has constant reminders of her CW - in the naval columns and now in his presence. She has no closure - she sent her true love out the door for no real reason.

CB was also surrounded by loving, supportive friends and as you said, Anne is all alone in her grief. No one understands her pain over the loss of her love.

Also men were on the marriage market for longer so he had more time to recover from his loss and pursue another love.

I know I'm reading a lot into 17 words. :-)