You can tell the harsh truth in a funny/joking manner where it doesn't carry the same sting if you just said it strait. It's also all about the words you choose. You can also steer away from having to reveal specific stories and examples just by how you say things. If she asks about your family, tell her "yeah they're all crazy" but with a smile on your face then she doesn't know if you're serious or not. If she pushes the issue further, explain that you and some members of your family "don't understand each other".
The phrasing of that is important, not "we hate each other" not "we don't get along" simply, "we don't understand each other". Both people can both be good human beings and not be able to understand each other. When people fight or when people hate each other or don't get along, usually someone is wrong. Guys who blame their family for things seem spoiled and immature. Guys who accept the blame for their family's problems seem weak and spineless. So don't do either. Your family and your relationship with your family is reflective on you, so you want you and your family to seem good without having to directly lie about it. More importantly you don't want to spill all your problems on the table and have it turn into a whining, blaming, sharing of family issues. That comes after you're married.
~Antithesis
