Creepy faces Muriel made

I didn't notice this the first few times I watched it...It kind of blurred in with Muriel's strange giddy behavior when she was around the swimmer, but why was Muriel sticking her tongue out like a lizard during the scene where she meets the swimmer and during the wedding scene? Yes, she was weird, but sticking your tongue out is creepy. It isn't something you do when you are around an attractive guy you are trying to impress. During the scene when she first meets the swimmer, he looks at her in disgust, and in response she giggles, pops her eyes out, and sticks out her tongue, as if she is playing with a baby. I think she does it again at the wedding. When I noticed it the first time, I had to rewind it, making sure she really did that. Very creepy. Again, I know she is weird but that was very over the top to be written into the script. Who does that ?Oh well.