I imagine this forum is a better place to have an actual discussion regarding Brittany Murphey and her career (voice acting in particular).
Luanne is definitely one of my favorite KOTH characters. Everything that came out of her mouth during the classic years is pure gold. We quote her on almost a daily basis. The character may be a little hard to believe / over the top (like any TV character) -- But there are quite a few ditzy/clueless people like her out there.
A few memorable moments that come to mind:
When Luanne finds the cow skull in the field and thinks it's Peggy
The whole phase she went through after the death of Buckley with short hair.
When the guy in the photo store breaks up with her "Linda? That's not how you pronounce my name"
I've only caught a bit of the news coverage (just found out this morning) and have yet to hear them mention King of the Hill. I think more people know KOTH over any movie she was in. I guess it's just easier to show clips of her in movies rather than a cartoon character. Lazy journalism though.