THANKS VERY MUCH TO ALL CONTRIBUTORS
Oral sex is NOT a risk for HIV, and other STDs, there would be a very low risk. It's really not much of a concern. It's highly unlikely you would ever get an STD from performing cunnilingus. The best practice is to know your partner and ask about their health and sexual history before getting intimate with them, and if you're in a relationship with that person, testing together for all STDs is a good idea and a way to enhance the trust.
The general rule of thumb is that as long as you wear a condom for insertive sex (vaginal or anal), you are protected. Mutual masturbation (ie fingering) is not a risk of any kind.
Don't be frightened away from her sweet spot. Unless she actually has an std or you actually have one, there is no inherent risk to licking her vagina or clitoris. If she doesn't want to tell you whether she does or doesn't have any stds or infections, just refuse to do anything. It's her loss anyway, and if you are her partner, you deserve to know what you're getting into. If you are unsure whether either of you has an std, get checked. All it takes is a visit to the doctor.
It is possible to contract diseases from doing this, as it IS and exchange of bodily fluids. A solution to this worry is as easy as placing a piece of plastic wrap over her vaginal area, creating a barrier between your mouth and her vaginal area. Do not use your fingers internally unless you want to use a pair of exam gloves. And, of course, wear a condom. Go for a shower after sex. Silly as it sounds, this is the safest way to go about this with someone that you don't know their health history. - Blu PS: another solution is to NOT have sex with someone you are this 'afraid of' healthwise, which would be my choice if i were you.
It is not up to me or any other professional person, but if you have any STDs, AIDs, or HIV, and you don't tell your partner, you're up for some charges since it is illegal to hide that stuff. The risks are STDs. It is safe if you both do not have any STDs