Why did it say this...?

So I'm good friends with this girl..Anyway at prom we took pics together..She has them on her facebook...I was looking at them and under one of them one of her friends said "Well by looking at (my name) lips, and your lips being smuged we all know what you two did all night long...kissy-kissy, smoochy, smoochy..know wonder we didn't see you" then she responded back saying "shhhh...." What does that mean?