To clarify what I wrote earlier - as this is a Y7 or y8 workshop, in an all girls school, I would in the first instance expect something that needs delicate handling initially (remember many of the girls may not yet have started their periods, may not be well in the swirl of hormones that puberty delivers, may not yet really have started to think about sex or boyfriends/girlfriends/etc, and one would hope that very few of them, if any, had actually had sex, so for many it will be at a point where sex and relationships are still abstract conceptual things).
If it was an LGBT session and the only LGBT session being run in the year amongst other PSHE (sorry, can't remember exact title) sessions, then I would expect it to spend much longer on the basics, and to spend much longer on the LGB part rather than the T part as statistically you would expect that to be relevant to many more people there given the proportion of LGB vs T in the general population.
I would expect the topic to be covered again as the dc progress through the school and as you can explore the ideas in more depth as the dc get older and more able to deal with the discussion. But initially I would expect one of the younger friendlier nicer accessible female members of staff to run the workshop, certainly not an external person that came from a biased pressure group.
Workshops with role models from particular communities is great - but probably not until about y9 or above.
And if any child is in a workshop and feels uncomfortable in the way that your dd did, they need to be able to leave and talk to a sensible adult to raise the safeguarding issue at the time. If children who are normal, sensible, active participants in class (as opposed to troublesome kids that do anything to disrupt - big sweeping generalisations I know) are worried about participating for fear of being punished for asking perfectly reasonable sensible questions then that's terrible. And as I said before - making everybody say the gender they identify as at any age - let alone at such a young age - and then writing it up on the board is a dreadful thing to do.
I really hope that you have success making the school understand quite how appalling this is and what a failure of their safeguarding processes (not to mention the trust that parents and pupils put in it) it is. And I hope that the Easter holidays don't get in the way so that the complaint is lost - and that they manage to do something to rectify the situation...