Vagifem is a low-dose ‘localized’ estrogen. It is delivering estrogen to the vagina and adjacent tissues, but not to areas outside of this area (that's why it's called 'localized' vs. 'systemic'). This is a great choice for maintaining vaginal health, since estrogens improve blood supply to the area.
By the way, Vagifem has just come out with a lower dose — 10 mcg as opposed to the typical 25 mcg — that seems to work just as well. There is another prescription alternative: a low-dose ring and cream to deliver estrogen to the area.
An over-the-counter option could be vaginal moisturizers used consistently. Moisturizers don’t improve blood supply, but they do work to keep the vagina moist and supple. You might also benefit from a lubricant during sex.