The first thing that I think of when an animal begins to suddenly drool profusely is that they ate or chewed on something irritating. Secondly, if something is going on neurologically, they may not be swallowing their saliva like they normally would. Also some medications and such could cause excess salivation. This issue is complicated by the fact that she doesn't want to get up an walk around. If she seem slightly "out of it" it could possibly be a mild seizure or pre-seizure state. Unfortunately, motrin can also be something that is not handled well in dogs - especially little ones.
Since she is so little and therefore can't handle a lot if the motrin may be a problem or she ate something irritating or possible poisonous, I would recommend you contact an emergency veterinarian tonight. It may not end up being anything, but with these little guys you don't always have as much latitude as you do with the larger dogs.
You could try giving her a little Karo syrup on her gums, as hypoglycemia is fairly common in the little dogs. This can cause them to seem very dumpy and could possibly cause some drooling.
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