I am a college student. My girlfriend is very fond of to make me doing oral sex (cunnilingus) & anal-oral sex on her. I like it very much. But sometimes she discharges a white-coloured fluid in my mouth. I like it for imbibing, but my question is, “is this vaginal-fluid harmful to me”?

No it’s not good as it may contain microorganisms like bacteria, fungi etc. Vaginal fluid is not as sterile as semen.