It does sound like you've got issues over control JG! This is a key part of her life, where she does start to become independent of you. You may not like her best friend, but it's her choice. I have this with DS1, who still remains joined at the hip with his best friend and they're 14!
Once they're at school it doesn't matter what happens at lunchtime - you are not there and have absolutely no control over what they eat. And don't think a packed lunch gives you that control, because they all swap their food! That nice, healthy, wholemeal sandwich you sent in will quickly be swapped for white bread and jam!
Over the years I've learned to ignore school meals. I consider my job to provide good, healthy meals at either end of the day. So I think about their 5 portions in terms of what they have at breakfast and at dinner. (Not that they always do have the 5, I'm no saint )
DS2, who started secondary school last September, initially had school dinners, which was hugely liberating for me - no having to make that packed lunch! - but has now decided he wants a packed lunch. I have agreed to this but only if he makes it himself, which he has agreed to do.
Also saves me having to fumble around for £4 in change every day! (£2 for each son)