I mean, she might like him. That's one possible explanation here, given she said she waited for him so she could say bye before running off. However that's still quite inconclusive, given we don't actually know that that's the reason she was there. For all we know, she could have just been there for other reasons and then was laughing because she thought she was just making a funny joke to him. Or, going even further, she could just have decided to mess with the guy to see if he thinks she likes him. Needless to say, we're going to have to run more tests here to draw any definite conclusions.