Remember when you were younger and you'd spill a drink or food on the carpet you'd suck it out. Yeah I know you shouldnt have because of the microbes living in there but you did it anyway so fuck off! You could do the same thing with her hair ... might be a little weird but I'm sure she'll be happy he hair wont stink of whatever that is. Although now it would stink of your coffee breath. That's better, right?
Or she'll kick you in the balls and run out of the restaurant splashing the rest of diners in the face with whatever soup that is.
Either way you're stuck with the bill so fuck it.