Hi Jane,
Sorry to hear of your sister’s diagnosis.
As others have said, it does very much depend on the hormonal status of the cancer. If it is strongly oestrogen receptive, then HRT will unfortunately be a firm “ no”. If it’s not hormone dependent, then I can’t see why your sister cant continue with her HRT.
I have oestrogen + metastic BC, so no HRT for me either. I take Veozah (fulvestrant) the non hormonal drug for hot flushes. As bomb mentioned, it is only available on private prescription but it doesn’t address any other menopause symptoms.
After my primary BC, I went to see a very well known MS and she prescribed me HRT. We had an adult conversation about benefits and risks etc.
So, for your sister, HRT may not be off the cards permanently; just via a GP.
Best of luck.