Why would a girl squint her eyes when I talk to her?

I was recently hanging out with a female friend and it seemed we had a great time and great conversation. I noticed something though, when I would talk to her from time to time she squinted her eyes at me and we were sitting across from each other. I also noticed when I was talking to her one time she sucked in both of her lips. I made a couple jokes and it seemed she laughed hard at them. Are these signs she is interested in me?
Why would a girl squint her eyes when I talk to her?
Post Opinion