Before Susie Green started running Mermaids, she worked for the CAB as an IT manager. She has no professional or educational qualifications in this area at all, to my knowledge. Entirely self-taught, and absolutely determined to justify the choices she made for her own child and enable - some would say push - other parents to do the same. She does this on the basis of extremely questionable assertions that if children can't transition they will harm themselves, plus of course the entirely unevidenced view that gender identity is innate and sometimes the body needs medical treatment to match the brain. They no longer say 'born in the wrong body', but they did, for many, many years.
When her eldest child was very young, she and her then husband were taken aback at the child's fondness for 'girl' toys and clothing. They appear to have made an absolute pig's ear of handling this. Instead of accepting their child's personality and preferences and recognising and working on their own sexist attitudes and prejudices, they took at face value the poor kid's statements that God had made a mistake and the child should have been a girl.
SG threw herself into the task of ensuring Jackie would be one of the youngest UK nationals ever to have hormone therapy and sexual reassignment surgery. She took J to the US to get puberty blockers and cross-hormones when J was 12yo. The NHS wouldn't have gone near that at the time (15-16 years ago now, I suppose). She took J to Thailand for surgery, which was carried out on J's 16th birthday, the earliest time it could happen legally at the time. Thailand has since raised the minimum age to 18.
At this time, Mermaids was a tiny obscure charity set up to support the parents of gender questioning children. They used to accept the NHS line that watchful waiting was the way to go, given that most gender questioning children accept their sex as they go through puberty. SG has been the main driver in moving it away from that and putting pressure on GIDS at the Tavistock to go for instant affirmation and hormone treatment, as young as possible.
In my view, she has a good deal to answer for, and I'm not surprised she doesn't want to debate with Transgender Trend. The house of cards might all come toppling down and then where would she be?
Here's her TED talk, setting a lot of this out. www.ted.com/talks/susie_green_transgender_a_mother_s_story?language=en