I actually volunteered on a rape crisis hotline (I am a cis woman, if it matters, and yes I'll call myself what I like, thanks) and I would be 100% happy to speak to a trans woman in any therapeutic or crisis context. It wouldn't even cross my mind to think otherwise. And yes, I have been sexually assaulted by a man - a white man, in fact, and I would also happily deal with a white person in a therapeutic setting.
As a rape crisis hotline volunteer I actually dealt with a victim who used racist language to describe the man who raped her. I told her I understood she was upset but that I needed her to please not use that word and then she went on a tangent about how 'not all blacks are n-words but this guy was' (it's a thing that particularly racist Americans love to say).
I found myself, as a Black woman, feeling upset and less able to help this particular woman, so I re-iterated that her language was unacceptable and that I would be passing her call to another colleague. That other (white) colleague also asked her to use "black" instead of "n*er" and I think she agreed, though it was a while ago. If she hadn't agreed and had continued using that word, my colleague would have probably still tried to help her, but she certainly wasn't obligated to do it.
If I were a trans woman, I wouldn't want to work with someone who had a phobia or hatred of me, just as a Black woman, I wouldn't want to work with someone who was blatantly racist towards me. It's not going to be a useful therapeutic relationship for either party. But that doesn't mean that the victim gets a pass on her phobia or hatred. If she politely said "I prefer to speak to someone who isn't transgender" and she was in active crisis, probably would be best to skip over that - but if it kept coming up or she used slurs or if the only person available wasn't a cis woman, well, same thing that would have happened if there were no white colleagues available to help my racist counsellee - you either get over yourself real quick-like and take the help on offer without saying nasty shit to the people trying to help you, or you go somewhere else for help. Being a victim doesn't give you the right to victimise someone else.
Yes please do go ahead and pile on, I know you all disagree with me and some of you will probably think I'm some kind of monster. Luckily most decent and reasonable people won't agree with you and I'm writing this mainly for the people reading this who might think that every woman in the UK hates trans people - no, it's a very specific and noisy minority that gather here to shout into their echo chamber. Their noise is massively disproportionate to their actual size, thankfully.