Well, if the condom were the extra large super duper size and you weren't filling that up snugly, I can certainly see such spillage out of the condom happening. (try the next lower size condom? else a snugger line/brand)
If you felt semen at the base of your condom and some in your public hair, for sure some at least got wiped on her exterior moist areas (and that could do it) and some may have also been pushed just inside (that could also do it, and even better).
While it just takes one, the odds of merely one sperm doing the job under those circumstances is astronomical (1 in 1,000,000 perhaps), but spillage involving several drops on her moist labia (sperm can't travel over dry skin but moist skin's fine), well, a few drops is likely 10,000 - 50,000+ sperm. Not the full load of tens of millions, but still enough to be a credible threat, hmm? Wildly guessing: 1 in 300 chance.
However, if you were totally confident that you came outside her, of course there ought to be no risk, condom spillage not having a chance of being in contact with her.
I pulled out and then came probably 2 seconds after, so I think I should be fine.