If we look at what SG said about her own child, Jackie, it sounds as if he was very like @AtalantaRun describes. SG says she herself was fairly relaxed about this, but she did jump to the conclusion that her son might grow up to be gay, which suggests she wasn't taking it entirely in her stride. To be fair, depending on where you live, the circles you move in, and what your family is like, a gender nonconforming boy might well attract a lot of comment, some of it very unpleasant, so I think it would be difficult to remain completely relaxed about it. Anyway, the real kicker in that family, by SG's account anyway, is that her now ex-husband was not happy about Jackie playing with dolls and dressing up. He had expected his son to be interested in sport and rough and tumble - the phrase 'real boy' is coming to mind here - and so Jackie must have been a disappointment. I really don't think it can be overstated how devastating that can be for a child, to know that something absolutely fundamental about yourself is somehow wrong and repulsive to your own parent.
If this had happened in my family, I hope I would have had the strength of character to put my child first. Unfortunately, SG didn't. She and her husband ended up at marriage guidance because there were so many arguments about Jackie and she says the therapist said 'Just take the dolls away' so she did. This pleased Mr G but had a catastrophic effect on Jackie, whose mental health all through school appears to have been on on the floor. It took SG's mother to convince her that Jackie should be allowed to have a doll again, but (incredibly to most, I would hope) SG by this time had decided that Jackie wanting a doll was not just a small child wanting a doll - it had to be a sign that there was something wrong.
Jackie had by this time very understandably started saying he wasn't a boy, he was a girl. He was a tiny child constantly being told 'Put that down, you're not a girl!' In his mind, of course he was going to conclude that the only way to get what he wanted was to be a girl. SG was somehow unable to see this. She took Jackie literally and did 'research', i.e. looked things up, and concluded, yes indeed, a child could be born in the wrong body, and now there were medical treatments that could correct this unfortunate birth defect. She has no training in medicine or any other health care discipline. She has no science or psychology degree as far as I'm aware. She was working as an IT manager at the Citizens' Advice Bureau. She wasn't qualified to interpret or assess the research. She took from it what she wanted to find, and acted on what she had decided would be best for Jackie, which at the time was in total contradiction to the watchful waiting approach GIDS and most gender specialists around the world would have advocated.
So poor young Jackie was socially transitioned at an early age, taken to the US for puberty blockers at about 11 or 12, and whisked off to Thailand so he could have sexual reassignment surgery, i.e. castration, on his 16th birthday. How she wasn't prosecuted for that is beyond my comprehension. A parent taking a daughter abroad for FGM would be prosecuted (I hope). How is this different?
And along the way she got involved with a tiny parent support group called Mermaids, and the rest is history.