How likely is it that a non-medically trained woman could perform oral sex on a man, spit semen out & use it to successfully impregnate herself? i have reason to believe a girl i was dating may have actually tried this & i hope it's low probability.

A thing called trust: Any way imaginable that gets some fresh semen to the inside of the vagina can start a pregnancy (a new baby, family life, etc...). Human imagination is limitless. Fertile couples having sexual activities base decisions on trust and faith... we hope. A good rule is not to squirt any sperm out anywhere near another person unless there is mutual trust and common goals.