Okay, so to be sure I understand - the girl touched her rash, then touched your hand?
Even if her rash was herpes (which is doubtful, but let's assume for a minute that it was), herpes doesn't infect your hand, especially the outer part of it. The skin there is too thick to penetrate. It also dies quickly when exposed to air.
I have no idea if her reputation is true (and most of the time, reputations are not based on fact, but on rumor, so don't be the guy that repeats that stuff), but even if she's slept with a lot of men, it doesn't mean she has herpes. Lots of promiscuous people don't have STDs, and lots of people who've only slept with 1 or 2 people do. I got herpes while in a long-term, serious relationship.
You can resume all normal activity. You can masturbate, touch your girlfriend, etc. You don't need to check anything, wear gloves, or anything else you've thought of.
I don't know if this over-reaction is based on not having information, or if you have a serious fear of germs, or anxiety or OCD. If it's a germ fear, anxiety or OCD, please talk to your doctor. Ask for a referral to a counselor and talk about medication, and if that's appropriate for you. (I say this with compassion, not criticism. It must be hard to live life with this much fear.)