"Transphobia" won't be what's stopping doctors from using medication for the purpose for which it was developed.
Unfortunately,"safe" use of puberty blockers is not that simple. They have huge side effects, even in use cases like precocious puberty. Every case will be looked at differently so that doctors and parents can weigh up the risk benefits. In some cases, doctors will recommend that the risk (of the horrendous side of effects, some of which won't appear until later e.g. osteoporosis) is too great for the likely benefit for that particular child.
If your daughter is struggling with precocious puberty, that sounds tough. But it's never going to be a simple case of PBs being the automatic answer. How old was she when her puberty started - and what were the signs that it had? What age did her period start?