Hiv seroconversion illness after orogenital contact with successful contact tracing. Orogenital contact and the isolation of neisserioa gonorrhoeae, mycoplasma hominis, and ureaplasma urealyticum from the pharynx. The risk is probably the same whether you swallow the semen or spit it out. New york: mcgraw-hill; 2008;1277-1308.
Oral sex isn’t a strictly human activity, as you can see here, it is practiced even by animals. Even if her viral load is detectable, this carries a very small risk, which can be reduced by holding a latex barrier over her vagina.