I would say...

1) Call her whatever you feel like. It is your feelings that count most.

2) I would say don't mix the circles. Ever.
Some people were born to be intolerant and there's nothing we rest can do.
Given that some others are just misguided, just tell your girlfriend to remind them of the harassment not only of same-sex couples, but of interracial couples (which imho is a bit closer in analogy - same-sex are "couples of equals" in ways in which interracial couples are "couples of unequals" - socially speaking; I do NOT consider people unequal based alone on either race or age). And of the Golden Rule - do not unto others as you would not have them do to you. If you are not breaking other people's relationships apart, why should they break yours apart?
On top of that, who matters are her parents. If her parents are OK, whatever everyone else says is overriden.

But of course, some of us have been more burned than you seem to have been. Plus you know best. You know more about the situation than anyone of us does.