Because Emma had survived the Abuse decades ago when she was married to Ethan, because she had precisely examined it; she knew the ‘moves’ as if it were a ballet.
She knew he would lure her to his City for some benefit or gift or something that she could not say no to.. She knew he would make it uncomfortable for her.
She knew… hence….
Emma expected that instead of a flight which left mid morning and arrived mid afternoon, he must find a flight which left at 2 am so she would arrive at 6.
This is because during the years they lived together, Emma had always had difficulty waking before 10 am.
He had known about getting her benefits from the previous spring, but knowing how she hated the cold, made sure to send for her in February.
Emma made no reaction to the early morning flight or that he scheduled it during the coldest month of the year.
This is because Emma expected Ethan to try to make her as uncomfortable as possible.
Had it been a flight leaving in the late morning, or set in the month of June, Emma would have been off balance. It would have made her question her analysis. Perhaps she might have been lured into believing he had changed, or she might have left herself vulnerable.
But from the moment she got the ticket in February she knew she had it all in place.