Sometimes it is hard on kids this young to be removed from old friends. The fact is though that unless you can set up a play date at least once every week or two they are going to drift apart regardless. While it may be fun to meet up again......she will likely just get upset all over again when she finds that it will be several weeks or longer before she sees them again.
The good thing about children is they are resilient. They tend to cope far better then adults and often learn from these types of situations. By taking her back every once in a while you are prolonging the inevitable. Eventually it will have to stop......can you imagine once a week visits once she learns that she can see them? And the fact is, if she learns that its a simple car ride away she will start begging and pleading to go....putting you in a difficult spot.
While it may seem easier to make the trip, at the end of the day it is going to prolong the pain for her. Encourage her to play with her new friends and get her involved in a new class if you can. This will help once she starts making new friends.