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Benzocaine has the potential to cause serious problems in cats, but less so in dogs. Of course your dog is very small so we need to be cautious. However from what you’ve described I think it’s highly unlikely that she has swallowed enough to cause toxicity.
From what you’ve said I presume that more than a half hour has passed since she licked your lip…if that’s the case then it’s too late to induce vomiting anyway.
Don’t get too worried, I feel the risks of a problem are extremely remote. Keep a watch on her over the next 24hours. If you notice any signs of ill health then get her to your vet. In particular watch for her being off her food or signs of weakness or incoordination.
Kindest regards, Peter