If you've seen the Blooper reel as an extra on the Season 2 DVDs you'd find that out.

Obviously at some point Suzanne adopted it to use in a more exaggerated fashion for the Chrissy character.

But yes, she snorts when she laughs.

I believe this is her really laughing, snorting like nobody's business.

https://www.youtube.com/watch?v=M3ZSN6KtTps