This is a very low risk activity. Assuming she is HIV +, and assuming that she has a serious cut/ bleeding wound in her mouth is too much assumption. Even if that is the case, our saliva will render HIV intranmissible mostly. So you need not worry. You risk is vanishingly small. Chill.
The Hiv virus is not present inside saliva. This is why you've read somewhere about traceable amount of blood, which does carry hiv.
In practice, there is no way you could have been infected.
Unreasonable fear is linked to paranoia and psychosis.