Yes and they are things to think about. What did LE or the press specify? Did they say "called" or something more ambiguous like "contacted by cell phone?"
On the other hand, I think AB had plenty of time to do what she intended to do, especially if she had done preparation beforehand. Someone else mentioned that they thought she was killed at that site - I agree. I think its possible AB offered to walk her home because of her fear of the dark or followed her and/or led or forced her there, possibly at knifepoint.
Remember LE has said that Elizabeth was killed around the time the call was placed and that location was "several hundred yards" from the house. I'm guessing 10 to 20 minutes to get to the location and less time for AB to get back.
LE would also spend some time with Elizabeth's mother getting info.