Not my partner, and I'm not T1, butwhen my mother was given a similarly devastating diagnosis (no timeframes offered in her case), it took a bit of getting to grips with, in terms of simply learning to live with that dreadful knowledge.
My relationship with my mother had peaks an troughs, but I promised myself (ans silently to her) that I would do what I could to make her remaining time as comfortable as I could and to try to make happy memories, for us both.
As suggested by others, please do reach out to MacMilllan - for yourself, as well as your wife. Mum's Macmillan nurse is a wonderful woman who helped us both in so many ways, both during her lifetime, but also beyond.
Mum's MacMillan nurse suggested Mum attend the local hospice as a day patient, which Mum reluctantly agreed to. She hated the idea, but actually really enjoyed the experiences, to the extent she was content to accept some respite care on a couple of occasions. Whilst there, some of her meds were tweaked, but it was just a really positive and pampering experience. She would have her hair and nails done, and would be offered a sherry before dinner in the evenings! Great place.
I can't pretend it was a pleasant, or easy journey, escorting my Mum to life's exit, but on reflection I am so grateful we had that knowledge to do what we could, and it allowed us to become really, unexpectedly, very close.
I hope you and your wife, and extended family can make good memories and that her journey is as she would hope. Reach out whenever you need to.