Often when I’m first talking to a girl, she moves her lips in a way so the top and bottom are less visible. Almost like they suck them in for a second. What does this mean? Is it a good or bad thing in your opinion?

Picture, this is the best I could get: https://imgur.com/a/W0QC3E7

Knowing this could help me from closing on girls who’s body language shows is not available.