It's not that often that you get a T1 using just a background insulin for as long as you have not unsual though at the very begining and throught the honeymoon period...
My persons view on the insulin you suggested..
Mixed insulin
The pro side of this is the 2 injections a day, but saying that it only really effective if the persons leads a very regimented lifestyle, both in activity and food intake, greatest advatange to the older generations within a selected group, not really for the active retired
Basal/Bolus
Cons.. Requires more injections per day, and have to learn good carb counting and monitoring/data regimes to get the most from..
But the pro is that with good carb counting, good monitoring/data regime and understanding this becomes a very flexible regime to use, enabling the person to match control to their daily needs and as required..
Given the choice I would never go back to the mixed insulin regime, this was the first type of regime, didn't have the pre-mixed insulin but used to mixe background/quick twice a day, following the regimented regime of the now pre-mixed insulin..
If you feel happier gping down the Basal/Bolus route, I would enlist your sister help, so that you then explain to your consultant the 'whys' you feel this is better for you than mixed insulin..