Dear Mother-in-Law,

It was a shame you had to stay here for such a short time.  I thought I might have coped, but it was unbearable seeing you leave.  The relief was immense when I heard we might see you again soon.  I wanted to end it all by saying goodbye now.  I hope I will not have to say it to you again for a long time.  If you have the opportunity to spend Christmas elsewhere next year, please do not.

Much love

Matthew