I've just Googled "Roisin Murphy trans" and been taken to a queer/music forum called Popjustice.com
Page after page of tearful and rageful (often both which I find makes you cry thru your nose) invective.
I'm now certain she left the comment, anyone else would have PR back tracking like a mad reverse somersaulter on acid.
She's taking some risk here. Alienating a large swathe (the majority?) of her fanbase quite possibly.
I suspect her radio silence since the FB post is to just see the lay of the land, and assess collateral damage.
The truth? She may have been a gay and queer ally. That was fine up to a decade ago, when LGB organisations pretty much didn't (at) all sign up to the TQ+ agenda.
But as someone growing older as her success has mounted, she will have seen all the things we see, and pulled back.
In the modern age, it's extremely easy to lie, obfuscate or plausibly deny.
In the modern age, it's very hard indeed to be truthful to yourself and then be truthful to the world.
She's made a very brave step indeed.