What should I do?

Here is the situation I have been noticing my friends sister more and more often so I have a wedding to attend in 3 weeks so I asked her out, she agreed without hesitation.  So about 5 days after asking her to accompany me I shot her a message like this.

Me - hey how about we go out sometime this week so we are more comfortable around each other for the wedding. Heads up I will suck at dancing if you are looking forward to that.

Her - Hey,
I can't this week.
But I also need to ask, we are just going as freinds right? I know that that prop. a yes, but I had a lot of guy friends who asked me to stuff like this and then read too much into. So I'm just double checking. I don't feel uncomfortable, we're friends.

I would like to not be friends and shoot for an actual relationship, would something like this kind of destroy my chances. I need input from all those ladies out there.

So should I message her like this?
'Tell you the truth I did not have the intention of going as friends, I do have the impression that going as a couple would be nicer. What really would be the harm if we tried to date for a bit?'

Problem number one:  the idea that a sweetheart is not a friend.  The alternative is that you will marry a stranger or an adversary.

Message her like this:  listen bitch, we barely know each other. This is a nice thing for us to do; I'm not planning to bend you over in behind the salad bar, Jeesus.  So, just forget it, bitch.