No reason why being diabetic should stop you having HRT. Of course , there can be other medical reasons why you shouldn't, but being D isn't one of them.
What Sue says is perfectly correct - I was 45 and went straight onto HRT (cos my ovaries went in the bin as well) but I was taken off it in my late 50's and have had far more trouble with my remaining lady bits since that than I ever had before.
My eventual menopause wasn't all that bad - a couple of half hour-ish hot flushes a week but nowhere near what some folk seem to go through.