What does it means when my 4 month old baby has water like liquid coming out here mouth?

Mgt: She may be drooling, and the watery liquid may be saliva. If she is having any trouble swallowing, breathing or looks unwell, I would advise taking her to be seen in the ED.

Hard to say: This could be drooling, but without more information, I can't say at this age. It would be a god idea to sit down with a pediatrician and talk about when this started, what if anything, makes it better or worse, and if there are any other symptoms associated with this liquid coming from the mouth - sore throat , difficulty breathing, fever; this is an unusual finding in a child this age, see an MD