So according to that call, the crime alleged is 'use of words or behaviour to stir up hatred on the grounds of sexual orientation'.
IANAL but looks like this is referring to Section 3A of the Public Order Act 1986 as modified at a later date... www.legislation.gov.uk/ukpga/1986/64
"A person who uses threatening words or behaviour, or displays any written material which is threatening, is guilty of an offence if he intends thereby to stir up religious hatred or hatred on the grounds of sexual orientation."
"Threatening", "intends" and "hatred". And "sexual orientation". Those are the words that would have to be proved if this were to come to anything. They're not meant lightly in the legislation, if you read subsequent notes. It seems that you can accidentally stir up hatred, no offence. You can deliberately stir up ridicule, no offence. Your words have to be actually threatening, not just disagreeable. Not that I'm saying KJK did any of the milder things either. And again, IANAL, just reading what it says.
I speculate that it's "lesbians don't have penises", and that they're alleging that she was trying to stir up hatred against that very special group of "lesbians who do have penises". And I further speculate that they're fishing, trying to get her to say something to indicate such an intent, because if they had proof of it they'd have arrested her by now. And I further speculate that it isn't going to happen as she had no such intent and she's not one to get riled or use words carelessly so that they could be misinterpreted.
I'm sure KJK will tell us all about it tomorrow if she is allowed. I absolutely trust based on what I have seen of her events and her communications that she has done no such thing, so good luck Kelly.