it all depends on the girl. she either likes you or is trying to be nice, test the waters with her and watch her to see how she reacts with other guys
to go with her and dance slowly
Shes in to you
sex!!
It could mean that they are wondering if you have asked another girl because they want to go with you and im a girl so this is what im thinking.
Sadie Hawkins dance
Date
slap her and say she is crazy. Slow dancing these days is rude.
you "fast dance"
If you know that she likes you and she asks you to dance, she is just trying to get close to you. Dancing can also be very intimate so she might want to be close in that way as well. Is that really so hard to figure?
It means she she should probably like older guys.
No, because what if the boy asks a guy and what if the girls asks a girl? So the answer is no, but it depends on how the person will look when asking the question.
They like you