What to do about nozy parents and an un-oficially broken friendship?

Me and my (former) best friend have sort of parted ways. A little incident, graduation, both our changing personalities... well we don't really hang out anymore, which I'm fine with. A little happy, even. But what gets annoying are my parents always asking me why I won't invite her to this, or "why dont you ask (HER) to come with us?" and I'm trying to give them the hint, but they don't take it. And the thing is, if I tell them clean and clear, theyll question me all bout it and gossip and such... grr. Other problem, my brother is best friends with hers, and both our parents are friends, and they WILL talk, and the regression of our friendship isnt really official, even though we havent spoken in a month (its the summer holidays, after all) but I really want to avoid another fight, and her telling me im talking about her behind her back... but I also want my parents to stop bugging me about it. What do I do?