I had a somewhat similar thing happen to me with Adele although the email i got from her did not sound like a threat* was more like she was really sad but the thing that set it apart was the Bye at the end which to me sounded more like a Bye don't ever contact me again, and then i had to send her an email again explaining the situation with my deepest apologies to which she replied and to cut the email short she assured me that she's not angry at me but she was just sad.
As it has been said before her written English it's not perfect I don't think the email you got was a threat to you in my opinion it was her venting.
Now I've asked to set another meeting with her and she could not give an available date but if she gets anything in the mean time she will let me know, but I'm sure that after the cancellation we had I'm all the way to the bottom of the list.
Bottom line is she has to understand that things don't go according to plan sometimes and it's to be expected but that does not mean it's the end of the world, I know WG who had whole day cancelled by different people and she was cool about it.
