I found the girl ugly, so I stood her up
Why would you abandon her? That seems a bit rude.
You don't find her ugly?
You should not stand people up. Tell her to her face that you are not interested so she is not left hanging.
I don't have time for that.
If you don't have time to tell her that, then you should not be going on dates with anyone. You need to act more maturely with people you deal with.