Jo, when I was Amanda's age I would sit for ages with a pad a 3b, HB and 4h and just sketch away - it's where Becky gets her 'skills' from. We use to spend days scribbling. Amanda might just be a natural, and a pretty good one too.
Try not to be 'photographic' in what you draw - imperfections can make a drawing - less really can be more. Look up basic perspective, the horizon (eye-line) and lighting / shadows. If you want to draw people look up facial and body proportions, but here's a big tip, please look at 'carrot' people - if you can draw the shape of a carrot you can tweak it (them) to look like a person (people).
Please, don't give up.