I would start by asking her outright if she thought humans can change sex.
When the waffling begins, about gender and blah de blah I would define sex, very simply and press for an answer: sex. Not gender. Sex. Can humans change sex.
She will of course say no (because NOBODY) believes humans can change sex. If she says yes then a small biology lesson perhaps ;) pre GCSE stuff so not hard.
So once we’ve sorted that out I’d go on to the following points:
Women’s sports - I’d ask her if she thinks Amir Khan vs Wladimir Wladimirowitsch Klitschko would have been a fair fight. If not, why not? No of course it’s not fair. Now think of why men and women don’t compete (no penny, low testosterone doesn’t drop you into the same female bracket.) talk about contact sports.
Women’s spaces: why do we have them? What will happen if men are allowed in? Men, not just transwomen - men.
Women’s prisons: there are not enough spaces to safely isolate transwomen in the female estate.
Child safeguarding; what does she think will happen? I’d give examples from Guides for example and remind her that men have, and will, exploit any loophole they can to access victims. And what the public response will be to the first tragedy that happens due to lowered safeguarding.
Then I suppose I’d talk to her about the conflation of sex and gender. About how keeping the EA and reforming GRA/self ID sets up a massive conflict. About the importance of medical gatekeeping.
I’d probably end with asking her what she thinks about the fact that adults, predominantly men are pushing for demedicalisation while simultaneously pushing for medicalisation for children.
I’d talk about puberty blockers. About how dangerous they are. About how irreversible they are and how they set a child on a pathway that really doesn’t have an off ramp. And how suicide stats have been used as leverage because these drugs are so dangerous.
About how society sexualises young girls in particular and about how this plus narrowed stereotypes is leading to an epidemic of child mental health issues.
Will she listen? Goodness knows. Good luck with it Justine.
I reckon half an hour in a nice cafe with a few of the posters here and we could set out our arguments pretty well.