And he wasn't treated very well by his family as a result either. So you're kinda choosing between your family and leaving. Not saying you should always pick family, but for a young 20 something year old girl, that can be quite the ultimatum.
Most people end up doing something or other their family disapproves of - it's not some unusual hardship of adult life that outright prevents you from doing things. In his case, being both a doofus and a bit of a Nazi cut off the possibility of future family reconciliation. I suppose there's a line even in royal families.
Plenty of monarchs have done just that including her very own uncle.