Thanks for the query.
Vaginal blisters are a type of genital sore that develops in the outer area of the vagina .This could be because of a sexually transmitted disease
or chemical irritant, such as a soap or detergent that irritates the sensitive vaginal tissues.
Some women might also develop blisters in this area because of an excessive amount of friction without a suitable amount of moisture in the area, such as when engaging in intercourse while also experiencing vaginal dryness
So i recommend you to get investigations regarding STD profile.
Maintain personal hygiene, avoid chemical irritants like soaps, use lubricant for vaginal dryness.
Hope this helps.