My girl's left eye has been tearing since she woke up this morning. Should it be a source of concern?

Hi, I suggest you see a doctor as one can advise online about cold and mild coughs but not about a problem in the eye. Keep checking her if she is feeling irritation in her eye and trying to touch her ye or crying. These are the signs that she is having a problem and it needs to be addressed. Eye is a very sensitive part of the body and one can not and should not do anything unless one is sure about what is happening or one is a doctor himself. And do not worry, sometimes it is normal inflammation or can be a blocked tear duct that is a common thing in babies but in either case, you must see a doctor.