Well, that complicates things, Billijo.
A clever barrister should be able to destroy her credibility on LGBT issues with well placed but not leading questions. Same with any expert witnesses she hires. One obvious point is ability to parent is much more important than LGBT status to anyone without an axe to grind. A good barrister will demand proof of any claims to the contrary; I would think an unbiased psychiatrist's expert opinion trumps that of a social worker.
She can't act as her own expert witness because that is a clear and obvious conflict of interest. Any judge worth having will see that immediately. If s/he doesn't, your barrister will point this out and request disqualification on grounds of conflict of interest as an expert witness for your case. That might get her dander up, which is to your advantage.
Barristers are under no obligation to tell the truth, as witnesses are. They can question witnesses as they see fit. They can accuse her things like instructing your brother to to assault you. They can demand proof of any and all of your alleged transgressions. They cannot, however, badger the witness. Eliciting admissions of things the witness did is not normally considered badgering.