Hi, My Mum Has Recently Been Diagnosed With Scimitar Syndrome

Hi, my mum has recently been diagnosed with scimitar syndrome (which the doctors said doesn't require surgery, a hole in the heart (which they said they are going to operate on) and a tear in the wall between the chambers of the heart.
I've researched this tear and the only thing I can find is a Myocardial Rupture, which is supposed to only happen after heart attacks and have a very bad outlook, requiring immediate treatment and with half of patients dying within 5 days of a rupture. Yet this tear was discovered months ago and the doctors haven't been in any rush to operate (i'm not even sure if they are going to operate on this or just the hole in her heart). I'm worried they could be delaying because of the overcrowded NHS.
Is there anything else this tear could be and does the prognosis always have to be bad? What kind of an outlook does a person with this have?
Thanks for your time.