Welcome to the forum
Well it probably is, vinegar is quite acidic and I don't know if it's ever happened to you, but if you get vinegar in your eye it's pretty painful. Now even though snakes have toughened eye caps, I can't say that this would be pleasant. Have you tried placing your hand back in the vivarium with her on your hand? If she still won't budge, get a misting bottle and spray some water from about 20cm or so away. That usually makes them get off (same if you're ever bitten and they won't let go). I'm curious as to why you chose vinegar and not plain ol' water.
Salivating heavily and blowing bubbles sounds like an upper respiratory infection. Does she do this at any other times?
Vinegar isn't toxic but I wouldn't use it for that purpose. It's usually used for disinfecting enclosures or cleaning glass.
Oh and by the way, just to let you know since you're new, this belongs in the General Chit-Chat forum, this section is just for Cornsnakes.
I hope that helps
David