I think people are over-reacting. Suggesting you are neglecting your DD is beyond ridiculous!
I was probably fairly similar to your DD at age 12/13. Very headstrong and opinionated, quite capable of debate (probably more so when I was younger than I am now
and not afraid to express my opinions to adults I disagreed with.
When I was 12 I had a 16 year old boyfriend. He had l;eft school and had a 'motorbike'. I thought I was very cool. My Mum found out and immediately banned me from seeing him. I continued to see him in secret. However, 'seeing him' comprised of him metting me from the school bus everyday, where we'd have a 15 minute or so chat and lots of other people around and the odd 'slow dance' and fairly innocent kiss at the school disco. Sex was never mentioned at all and now I look back, he clearly wasn't very mature and I don't think it even crossed his mind. It certainly didn't cross mine. I was in no way innocent either, in that I was fairly worldy wise compared to my friends, but I can remember vividly being given a 'pill' by the GP for period problems and my Mum saying something about not to think it gave me a licence to do what I wanted. It took a while for the penny to drop, I had thought the GP used the word 'pill' to mean a tablet, not the pill.
My sister, who was pretty much the exact opposite of me really personality wise, very meek and mild and a people pleaser, lost her virginity aged 12 to a boy from school the same age as her. Subsequently, when she was almost 14 she started seeing a boy of 17, with my Mum's consent and interest, they spent most of their time at my Mum's house or his parents and they didn;t have sex until well past my sisters 16th birthday. They split up when my sister was 18 and she's since only had one more boyfriend, her now husband of 11 years.
I certainly wouldn't worry too much about your DD, but I do agree the best course of action is probably to invite him round to the house often and be involved in an interested/supportive way rather than forbidding her to see him. A lot of girls of this age are starting to feel they are getting grown up and by treating her as though you understand this, she is more likely to talk to you about things.