If i were to finger my girlfriend- who has herpes- how long would the herpes virus survive on my finger, and is it likely to die off if i wash my hand?

Depends: If she is having an active outbreak i would recommend not having sex.It will be painful for her and increase your risk. She may benifit from suppressive therapy like valtrex (valacyclovir).

Herpes genitalia: Patient is always at risk of sheeding even if not having outbreak. Incubation period could be 2-12 days, in some cases up to 26 days. The only way to avoid std is by abstinence. Latex codom is just a barrier to prevent std, patient can still get or transmit std when wearing a condom.

Short life: The herpes simplex virus is spread by close contact, so it means that touching a lesion (and not even a lesion) can infect the other person if the virus access a mucosa (mouth inner surface, or other similar tissue [glans, rectal lining]) or a cracked skin. The virus is fastly inactivated at room temperature and by drying.