Geez Louise.
It was just a thought about a way to read the letter that would resolve what seems like an oddity - the word abhorrent is very strong, but the rest of the letter doesn't really see to fit that. However you make sense of it, you are having to interpret the letter, no one here is reading it with some sort of magic objective knowledge.
As some of the comments said, it's a strong word to use about someone you are actively in a sexual relationship with, it seems to raise some pretty big questions about the relationship and why they are together.
But there is nothing about that in the rest of the letter. She clearly is ok with kink in relationships and seems to think that people should be willing to try out their partners kinks. She doesn't think though that they should have to try something they already know is a turn off. None of that is mind reading, it's what the letter says.
One way to resolve that is to say, well, she's got a moral problem with it but doesn't want to talk about it that way. In which case the real problem is a lot deeper, but that's not really expressed at all in the letter.
Another is to say, maybe by abhorrent she means something closer to "gross" which has the disgust factor without the moral element.