am i dumb did i pass up a good chance

Well my did and his girlfriend were going to go to town to go shopping and my dad's girlfriends daughter asked me if I wanted to come with them and I said no thanks she is about my age and what does that mean if aney thing does that mean she likes me or...

was she just being nice I am thanking I should have gone so I could walk around the store with her and shop and talk to her how can I find out if she likes me with out asking her I like her I thank she is cute and I would like to date her but I am scared to ask her becasue I do not want to be rejected o ya and one last thing I left out she is 18 and she is black and I am white what to do you thank about that well whatever advice you have I would really appreciate it thanks for taking the time out to read this

uhm, what would you do if your dad and his girlfriend got married?