When I read posts like this, I realise how different parenting styles can be.
This is very very different from mine. There would have been no peirced ears in the first place, but that is not the issue.
Missing p.e. for weeks 
I can confidently say that it would never have got this far, but if it for some bizarre reason it had got this far, I would limit every treat going, everything. There would be no tv, no playdates, no sweets, no after school activities, no treats whatsoever in any form or fashion at all.. until those bloody earring are out. Added to which, I would say, if I take them out before the end of the day, then she can get her ears peirced when she is 13. Otherwise it will be much later.
As for ruling the roost? It makes me feel anxious even thinking of that ever happening in my house. Just like my parents, they were most parents rather than friends. My goodness, you did not play around with them. On the other hand, they were the most wonderful, loving, consistent,msupportive parents I could have hoped for. Don't get bogged down in thinking that your daughter will love you more if you don't discipline her firmly. As my mother used to say, I am your mother first and foremost, your friend a distant second.