I think you should leave her where she's at. The teacher is a good match and she likes going to school. She already has friends and feels comfortable. A new school requires that she make a new adjustment. She may not get a teacher that is such a good match or one that she even likes. She will have to start over making friends. I suggest that moving her now will set her back both educationally and socially.
Yes, going to a different school will happen next year. But it will also happen to her friends and some of them, if not all will also be transferring. She is expecting to change schools next year. She will have a support system in place. When you move her this year everything changes for her. She will have major adjustments all the way around and be disappointed/hurt that she lost her successful start to the school year.
I also suggest that doing what is easiest for you is also very important. Your goal is to have a consistent, well adjusted way of living for everyone in your family. The stress of an extra driving time and other inconveniences will not only cause big adjustments for you but also for the rest of the family. Your adjustment is going to be a difficult one too. With a new baby, you and your family are already facing big adjustments. It makes sense to keep life as simple as possible.
After 50 years of living as an adult, I've learned that I cannot control most things in my life and that as long as I live consciously, everything does work out for the best. I suggest that just as this placement is working, whatever happens in the following years will also work out. If you move her now, you are allowing a move that could very well not work out. It seems to me that the negative and possible negative aspects of this move are not worth making the move.
I understand your concern for placement in future schools. At the same time, I've experienced rapid changes in school boundaries and policies. We just cannot count on the rules being the same next year as they are this year. so why take the risk?