So what's your sore spot?
In our case, it required two fairly committed parents (with regard to maintaining all of the languages) and an absolutely strict division of the languages: dh (German), me (English), and school (Swedish). It also required a fair bit of faith that exposure to Swedish only through school would be enough. It has been. If anything, German is the weakest language, but both can speak and understand it well enough that they have no problems communicating with dh's family and German-speaking friends, which was the main point.
I think it is a bit easier to drop a language if one knows that one of the other languages will still allow for communication between the family and the kids. In your case, your dd can still most likely communicate with most of your family fairly easily via English. In our case, the loss of English or German would have meant the kids being completely cut off from one side of the family or the other. It gave us the extra motivation, if you know what I mean.
I had the owner of the ballet place i was taking Hanna to tell me that if I pulled her out that it would be a huge mistake and that i wasn't parenting properly by not forcing and making her stick with the Ballet. She was only 4 at the time. My goodness. The reason i pulled her is because they were forcing her to wear makeup, no panties with this skimpy outfit for the performance, and basically said all children must attend the performance. I don't think so!! My child was in tears all the time because of the competition that was going on at such a young age. I thought Ballet was suppose to be a fun thing at this young age. Not at this place. I was also told by a few other parents that they felt that forcing their children into competitive sports at a younger age was good. That it was training them to deal with the "real world". My only pet peeve for now.