We moved our dd last year, beginning of year 2. Our dd like yours, liked the idea, but didn't want to lose her friends. After spending a day, she too loved it, but was happy to stay where she was.
We didn't say too much about it after the visit, but when the letter came through offering the place, we explained that it was a great opportunity and I suppose we put a very positive spin on it....i.e. extra sport (which she loves), lots of clubs at lunchtime, swimming pool etc. etc. We also said she would still be in touch with her friends and we would go to some 'key' school events at her old school.
After a day or two of not discussing it, dd said she thought she may like to go, so we went with that, and moved a few weeks later. We made a big thing of getting all her friends phone number (in reality there was only probably 3 or 4 that she would keep in contact with) and we gave her an old mobile phone with a Pay as you go, so she could contact them (she never has, but sees them at Brownies etc.,).
The move was great and it wasnt' until a few months in, she did start to mention how she missed her old friends, so we invited a few over to play and that was OK.
Now after a full school year, she loves it and wouldn't go back, but I think it took around 7 months before I felt she was fully settled and part of the furniture.
The differences in the education at our school are astounding and the difference in our dd more so, I am not an advocater of private education, or I wasn't, until I have seen what it has done and how brilliant it can be. I honestly think she has the best education now that she ever could. Our state was outstanding by the way, but not without problems, hence the move.
Year 3 is a good time to move, there will be a lot of other children coming from state schools into private at that stage (that was originally our plan), so she won't be the only new girl. You must be proud of her to get the part scholarship, but I know what it is like, the thought of moving and uprooting her. We didn't sleep for at least a week worrying!!!
I have to say however, that the thinking about it was far worse than the actual doing it and if I had known it would be so easy, I wouldn't have worried so much. Children are really very adaptable, although that probably doesn't help you much at the moment.
Best of luck.