Hello, I'm really sorry to hear of your mum's illness, regarding your query, I think the main question that needs to be clarified is 'what type of hospital does your mum attend i.e. is it public(Beaumont,Mater etc) or private(Bons Secours,Elm Park Private etc) or is it hi tech (Blackrock Clinic or Mater Private etc) ?
With Plan D cover, she is fully covered for all inpatient stays in all hi tech hospitals. With Plan B cover, there may be a shortfall cost of 260 per night in a hi tech hospital.
If she attends a public or private hospital, there would be no further costs involved, under Plan B, except for a private room in a private hospital.(price depends on procedure) .
Note: If you change from Plan D to Plan B and then a year later want to change back to Plan D, a waiting time of 2 years would apply for pre-existing conditions, so be very wary of all the implications involved.
Also, the accounts departments of both Blackrock Clinic and Mater Private are very helpful in explaining cover regarding Plan B - access to hi tech hospitals with Plan B cover has been opened up considerably in recent years, including cancer treatments.
Note, under Plan B, chemotherapy would be fully covered in hi tech hospitals also.
Health insurance plans are defined by the type or level of hospital cover it offers, rather than by the type of medical condition a person has.
I hope this explains things a bit clearer, my thoughts and support are with you both for the future.
Snowyb