Mother VS. Friend

Well apparently Eldest thinks of me as one of her best friends.. well kinda like a friend who is a mom.. you're like the cool mommy. Woohoo.
I am concrened
   First: Does this mean i'm to friendly with my children and not MOTHER enough? Like do I let them get away with to much?? I mean I know to some extent they are spoiled but..  they aren't bratty or anything like that, just over hugged.
   Second: I dont know... Im just worried that this si going to turn into the will you buy me beer situation.
  I know that Eldest and I have an odd situation being that I am her Bonus mom but she lives us most of the time. I think this is probably a good thing though for her and I. She is respectful and well mannered, sharp, helpful and all that stuff you'd like a daughter to be. But she is still fiesty a trait we encourage up to a point. I go to bat for her over certian things that she might be to shy to ask permission for. I am glad she see's me as a friend yet still an authority figgure.. Maybe the biggest part is that I make to encourage her relationship with Mrs. Ducky and she knows now (being old enough to notice) that I know im not her mommy and i am not trying to be. There are a lot of maybes.
The biggest thing I worry about though is are we skirting a border??? COULD this turn into a beer and tatoo thing??? Would I not see that coming until it's to late? Was this all because I let the girls have a biscut fight?? Or a sprinkle fight??? Or stay up late watching NCIS??  OR does this make me a good mom for worrying about being to much a friend and not enough MOTHER???  Will explaining that, her thinking of me as a friend but still a mom isn't always a good thing because im not her friend be enough??  Or in eldest's own way is she trying to say.. i love you very much??
Someone send help.
Love,
Eldests MEME