Hiya WTH, I know this is a bit late, and I hope you're not worrying about it at all, but I think fresh guacamole would have the same risk as pre-prepared salads, though I've never read/heard anyone say that it is a risk.

And apparently "Listeria infection in pregnant women is very rare in the UK, only affecting about one in 25,000 pregnancies." I imagine it might be even lower in Australia where most cheeses are pasteurised:
Eating cheese during pregnancy

This isn't enough to stop me eating pre-prepared salads or fresh guacamole. I figure the benefits of eating fresh stuff outweighs the small risk that there is of listeria. If you ate only cooked foods, you'd be eating hot chips most of the time!

And BTW my Japanese SIL said that in Japan docs recommend sashimi for pg women as the benefits outweigh the risk of listeria.

So I reckon a bit of guacamole is fine and probably even good for you.
xoxo