It's okay, girls are crazy, it's hard to figure them out.
And I'm a girl myself.
Doesn't sound like you really did anything wrong. I mean, unless you didn't ask it casually at all and was like "Hi, are your parents going to be home? ;D ;*" and if in the past you've only used her for sex or something... Then I can understand her side a little more.

If she didn't say whether the talk tomorrow will be good or bad, then it's probably bad, but it sounds like you know that already. Don't take it personally, especially if (IF) she's fucking around with your friends. There are always better girls out there.